Don't allow joins w/o source on an existing group. This is almost always pilot error.
Don't allow joins w/o source on an existing group.
This is almost always pilot error.

We don't need to check for group filter UNDEFINED state at t1,
because we only ever allocate filters with their groups, so we
unconditionally reject such calls with EINVAL.
Trying to change the active filter mode w/o going through IP_MSFILTER
is also disallowed.

Deals with the case described in PR 137164 upfront, cumulative
with the fix in svn rev 197132 which only calls imo_match_source()
if the source address family was not unspecified.

PR:		137164
MFC after:	5 days

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase