MFC: Don't look for GPT primary and secondary tables on a disk unless we have a valid PMBR.
MFC: Don't look for GPT primary and secondary tables on a disk unless we
have a valid PMBR.

Approved by:	re (kensmith)

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