When calling bioq_first() to see if a queue is empty in bioq_disksort(), don't save the return value as we won't use it.
When calling bioq_first() to see if a queue is empty in bioq_disksort(),
don't save the return value as we won't use it.

Noticed by:	Coverity Prevent analysis tool
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