[CI] Change rally and lower-constraints jobs

rally-dsvm-manila-multibackend and
rally-dsvm-manila-multibackend-no-ss were old
jobs whose definition was removed a while ago, however,
the check pipeline on this repo had these jobs
and this config error was not surfaced until
recently [1]. Replace these older jobs with the
correct ones.

The lower constraints job should only be run on
master, since it provides little value to stable branches
we've already shipped. We do not allow requirements
changes in these branches lightly. [2][3][4]

[1] http://lists.openstack.org/pipermail/openstack-discuss/2021-November/025797.html
[2] http://pyfound.blogspot.com/2020/11/pip-20-3-new-resolver.html
[3] https://pip.pypa.io/en/stable/user_guide/#changes-to-the-pip-dependency-resolver-in-20-3-2020
[4] http://lists.openstack.org/pipermail/openstack-discuss/2021-March/021204.html

Change-Id: I4a7de404bd02887e7a7b37fff8ce449846109cbb
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>

zuul.d/project.yaml

@@ -9,10 +9,12 @@
     check:
       jobs:
         - python-manilaclient-functional
-        - rally-dsvm-manila-multibackend:
+        - manila-rally-ss:
             voting: false
-        - rally-dsvm-manila-multibackend-no-ss:
+        - manila-rally-no-ss:
             voting: false
+        - openstack-tox-lower-constraints:
+            branches: master
     gate:
       jobs:
         - python-manilaclient-functional