Add default configuration for bugzilla and FAS
Update the utils function

- Use dogpile to cache user information and group information from FAS (up to 1 hour).
- Add method to update the Package owner in bugzilla when PoC changes.
Update owner in bugzilla when changing the PoC
Re-organize imports order so that pkgdb.lib.utils can use pkgdb.cache
Fix typo
Don't forget the import and to update the bugzilla when changing the status of a package.
Mock the function to set the new owner in bugzilla in the unit-tests
Add python-mock as requirement