This allows for cases where the requested project was something like
openSUSE:Leap:42.3:Update and the returned project was openSUSE:Leap:42.3.
With this change the fallback will be triggered and the global maintainer
will then be used.
Useful for determining if a request has an open staging project review
which makes it likely that it has been staged and avoids the need to
review each staging project.
Allows the code to be properly shared between checkrepo and
check_maintenance_incidents as a todo suggests. Given that the majority of
similar cases for code sharing are extension of osc.core it seems to make
sense to place them in osclib.core.
