Increase the 'all' timeout because slow tests are included

The default for tempest in .testr.conf is 500s. This was too short for
the heat slow tests so the time for that was increased to 1200. This
change is to a periodic job so if we need to it can be increased more
in the future.

Change-Id: If27ddef9865c54b997130c707382d2014d82e0a6
Merge "Increase the 'all' timeout because slow tests are included"