Add zuul.executor.work_root to inventory

It is helpful to expose the work_root into the inventory. Today, we
would need to use a relative path on log_root or src_root. Having the
absolute path is better to read for debugging.

Change-Id: I86ff459d283eaf348821c2f11c1f8575598f088d
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

doc/source/user/jobs.rst

@@ -322,6 +322,8 @@ executor running the job is available:
 **zuul.executor.log_root**
   The path to the logs directory.
 
+**zuul.executor.work_root**
+  The path to the working directory.
 
 .. _user_sitewide_variables:
 

tests/fixtures/config/ansible/git/common-config/playbooks/check-vars.yaml

@@ -13,6 +13,7 @@
           - zuul.executor.hostname is defined
           - zuul.executor.src_root is defined
           - zuul.executor.log_root is defined
+          - zuul.executor.work_root is defined
 
     - name: Assert zuul.project variables are valid.
       assert:

zuul/executor/server.py

@@ -1350,6 +1350,7 @@ class AnsibleJob(object):
             hostname=self.executor_server.hostname,
             src_root=self.jobdir.src_root,
             log_root=self.jobdir.log_root,
+            work_root=self.jobdir.work_root,
             result_data_file=self.jobdir.result_data_file)
 
         nodes = self.getHostList(args)