Review 26716

Robert Cowham
Rename P4MASTER to P4MASTERHOST for clarity with comments in:
- mkdirs.cfg/mkdirs.sh
- p4_<instance>.vars
- other files which reference
Remove unnecessary sed for p4p.template
#2: Change 26718 committed into //guest/perforce_software/sdp/dev/Server 7 0 0
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