(bug 45163) make gerrit's link parser not match incomplete words

It would be better to use something more sophisticated than \b to not
match within already existing links (like it was done for Bugzilla's
parser: Ib79728e9), but gerrit is using a DFA regex library which by
definition doesn't support any advanced regex features.

Change-Id: I93d1a978c366dfdf19a04994ba4df4ef16d6dc06
Merge "(bug 45163) make gerrit's link parser not match incomplete words" into production