calls callout_drain(9) to un-schedule a scan timer to prevent a page fault in softclock.
calls callout_drain(9) to un-schedule a scan timer to prevent a page
fault in softclock.

Submitted by:	sam
Reviewed by:	jhb, sam (original version), thompsa

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