afs-release: better info when can not get lockfile

For some reason this is failing in the gate -- the some reason bit is
hard to determine at the moment.  Log the exception.

Change-Id: I13c60c5dfc4ab19d8dec589c96338adc7461c992

playbooks/roles/afs-release/files/release-volumes.py

@@ -125,8 +125,8 @@ def get_lock(path):
     with open(path, 'w') as f:
         try:
             fcntl.flock(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
-        except IOError:
-            print("Unable to get lockfile!")
+        except IOError as e:
+            print("Unable to get lockfile: %s" % e)
             sys.exit(1)
         f.write("%s\n" % os.getpid())
         f.flush()

zuul.d/system-config-run.yaml

@@ -486,6 +486,7 @@
       - roles/
       - playbooks/roles/mirror-update/
       - playbooks/roles/reprepro/
+      - playbooks/roles/afs-release/
       - playbooks/service-mirror-update.yaml
       - playbooks/zuul/templates/host_vars/mirror-update99.opendev.org.yaml.j2
       - testinfra/test_mirror-update.py