Reinstate the assertion from r253045.
Reinstate the assertion from r253045.

UFS r232732 reverted the change as the real problem was to be fixed
at the syscall level.

Reported by:	bde

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