MFC rev. 1.21 to RELENG_6: fix module unloading panic
MFC rev. 1.21 to RELENG_6: fix module unloading panic

Approved by:	re(scottl)

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