Set currrel from input release if not Rawhide
For upgrade tests
need to set currrel and prevrel variables from output of
fedfind.helpers.get_current_release() only if release eq Rawhide;
and from release value if this one is a numeric value.
To be able to pass a non Rawhide url to scheduler,
and especially a Release that already passed GA.
Signed-off-by: Michel Normand <firstname.lastname@example.org>