Display only first 7 chars for git commit id

On the status page, if a job was queued via a timer or some way
other than a gerrit change id, the git commit id would be too long
for the change box. Limit it to 7 chars.

Co-Authored-By: Sergey Lukjanov <slukjanov@mirantis.com>
Change-Id: I4f54845675d11e4f76240cf4bf7b48f28f3e7d6a
Merge "Display only first 7 chars for git commit id"