rx: Process error queue after noticing errors

rx: Process error queue after noticing errors

If errors exist in the socket error queue, we will notice by a sendmsg
or recvmsg returning an error. If we never get an error, we don't need
to check the error queue. So, only call osi_HandleSocketError after
such an error has been returned, so we can avoid unnecessarily
checking the error queue when there are no errors.

Change-Id: I7c8aaaac42728dac7fb0634538b8cc317f0e7212
Reviewed-on: http://gerrit.openafs.org/8114
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Simon Wilkinson <simonxwilkinson@gmail.com>