Convert tempest-scenario-all job to tempest-slow

As per discussion on ML[1], we do not have any job which runs only
slow tests.

This commit provide a separate job which run only slow tests which can
be API or scenario tests. Further this job can be used cross projects
like nova, cinder, neutron.

Why we need separate job for slow tests:
 - slow tests create gate issues on job timeout which we observed\
   during Rocky cycle[2]. Not to effect gate let's start them executing
   on separate job.
Why to convert the tempest-scenario-all job
 - tempest-scenario-all job was created to run the slow tests along with
   other scenario tests. But slow tests can be API tests[3] and mixing them
   with other scenario or API tests is not good idea.
 - All scenario tests excluding slow tests are run as part of tempest-full
   job so let's not run scenario tests twice on gate.

[1] http://lists.openstack.org/pipermail/openstack-dev/2018-July/132527.html
[2] https://bugs.launchpad.net/tempest/+bug/1783405
[3] https://ethercalc.openstack.org/dorupfz6s9qt

Change-Id: I5b1d3041c0140bea11705ad287f1472e74aacb5c

.zuul.yaml

@@ -143,25 +143,24 @@
     voting: false
 
 - job:
-    name: tempest-scenario-all
+    name: tempest-slow
     parent: tempest-multinode-full
     branches:
       - master
     description: |
-      This multinode integration job will run all scenario tests including slow
-      tests with lvm multibackend setup. This job will not run any API tests.
+      This multinode integration job will run all the tests tagged as slow.
+      It enables the lvm multibackend setup to cover few scenario tests.
+      This job will run only slow tests(API or Scenario) serially.
 
       Former names for this job were:
         * legacy-tempest-dsvm-neutron-scenario-multinode-lvm-multibackend
         * tempest-scenario-multinode-lvm-multibackend
     timeout: 10800
     vars:
-      # 'all' is used for applying the custom regex below.
-      tox_envlist: all
+      tox_envlist: slow-serial
       devstack_localrc:
         CINDER_ENABLED_BACKENDS: lvm:lvmdriver-1,lvm:lvmdriver-2
       tempest_concurrency: 2
-      tempest_test_regex: (^tempest\.(scenario))
 
 - job:
     name: tempest-full-queens
@@ -353,7 +352,7 @@
               - ^tempest/hacking/.*$
               - ^tempest/tests/.*$
         - tempest-tox-plugin-sanity-check
-        - tempest-scenario-all:
+        - tempest-slow:
             irrelevant-files:
               - ^(test-|)requirements.txt$
               - ^.*\.rst$
@@ -363,7 +362,6 @@
               - ^setup.cfg$
               - ^tempest/hacking/.*$
               - ^tempest/tests/.*$
-              - ^tempest/api/.*$
         - nova-cells-v1:
             irrelevant-files:
               - ^(test-|)requirements.txt$
@@ -397,7 +395,7 @@
               - ^setup.cfg$
               - ^tempest/hacking/.*$
               - ^tempest/tests/.*$
-        - tempest-scenario-all:
+        - tempest-slow:
             irrelevant-files:
               - ^(test-|)requirements.txt$
               - ^.*\.rst$
@@ -407,7 +405,6 @@
               - ^setup.cfg$
               - ^tempest/hacking/.*$
               - ^tempest/tests/.*$
-              - ^tempest/api/.*$
     experimental:
       jobs:
         - tempest-cinder-v2-api:

tox.ini

@@ -135,6 +135,16 @@ commands =
     find . -type f -name "*.pyc" -delete
     tempest run --serial --regex '\[.*\bsmoke\b.*\]' {posargs}
 
+[testenv:slow-serial]
+envdir = .tox/tempest
+sitepackages = {[tempestenv]sitepackages}
+setenv = {[tempestenv]setenv}
+deps = {[tempestenv]deps}
+# The regex below is used to select the slow tagged tests to run serially:
+commands =
+    find . -type f -name "*.pyc" -delete
+    tempest run --serial --regex '\[.*\bslow\b.*\]' {posargs}
+
 [testenv:venv]
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}