Display message when overcommit-hook updated

To make the auto-updating feature more obvious, display a message when
the hooks are updated.

Change-Id: Id2c7d0a1a57a554ff80f3904da0642bbbf4cec1c
Reviewed-on: http://gerrit.causes.com/40971
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>