Make --repo-path an optional argument for db_recreate

db_recreate uses repo-path to call db_sync, but for db_sync this
argument is optional so it should be optional for db_recreate as
well.

Closes-Bug: #1279734

Change-Id: I68b0eb3c705525a047eb6bffe8d5e1b4b083cd91
Merge "Make --repo-path an optional argument for db_recreate"