auth: Make 'LocalUserCreated' hook non-abortable

auth: Make 'LocalUserCreated' hook non-abortable

Its return value was already not used. By using runWithoutAbort()
it means that if a hook accidentally returns false, it will throw
an exception instead of silently skipping other hook handlers.

This type of mistake has repeatedly caused problems in WMF prod
over the years.

Change-Id: I6af2261957eb20f18fa5f0d50c4c4835d3850cfe