When trimming memory to fit Maxmem, and we discard an entire cluster, make certain to subtract its pages from physmem.  Otherwise we end up running phys_avail_cnt negative, and bad stuff happens.
When trimming memory to fit Maxmem, and we discard an entire cluster,
make certain to subtract its pages from physmem.  Otherwise we end up
running phys_avail_cnt negative, and bad stuff happens.

MFC After: 1 week

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