Extract helpers from HookRunner methods

The `run_hook(s)` methods in `HookRunner` were a bit long. Extract
portions of them into helpers to improve readability.

Change-Id: I89acf7e23b3e44d11000fdda041622c3b2a19f2a
Reviewed-on: http://gerrit.causes.com/40385
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>