Rework the rl_encap failure case.  Previously, we would stuff the unencapsulated packet back into the IFQ.  Unfortunately, the only reason rl_encap would fail was due to m_defrag failing, which should only happen when we're low on mbufs.  Hence, it was possible for us to end up with an IFQ full of packets which could never clear the queue because they could never be defragmented because they were themselves taking up all the mbufs.
Rework the rl_encap failure case.  Previously, we would stuff the
unencapsulated packet back into the IFQ.  Unfortunately, the only reason
rl_encap would fail was due to m_defrag failing, which should only happen
when we're low on mbufs.  Hence, it was possible for us to end up with
an IFQ full of packets which could never clear the queue because they could
never be defragmented because they were themselves taking up all the mbufs.

To solve this, take if_xl's approach to the problem of encapsulation failure:
drop the packet.

MFC after:	3 days

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