Review 18915

C. Thomas Tyler
Enhanced p4_vars.template to support operating on an SDP-managed
host where no p4d process runs, such as a p4p (proxy) host, where
no /p4/n/root/server.id file exists.  The $SERVERID value will
be empty (but defined) in this case.

Enhanced to better support operating with replicas that share
/depotdata with their master servers, by making P4TRUST and
P4TICKETS values contain $SERVERID.

Moved SHAREDDATA from p4_vars to instance_vars, since it is not
inherently a global setting.  In sophisticated enterprise
environments, it can vary on a per-replica basis.  Adjusted
mkdirs.sh accordingly.
#3: Change 18925 committed into //guest/perforce_software/sdp/dev/Server/Unix 3 0 0
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