Simplify SDP version and deprecate SDP_VERSION and SDP_DATE.
Deprecate the SDP_DATE and SDP_VERSION counters.
Some changes needed:
* The p4_vars.template must be changed to remove REPL_SDPVERSION.
Change from: export SDP_VERSION="REPL_SDPVERSION"
Change to: export SDP_VERSION="$(cat /p4/sdp/Version)"
* The sdp_upgrade.sh will handle the new p4_vars.template during the
next SDP upgrade.
* The upgrade.sh will need to be aware of these counters.
* The SDP Health Check script will need to NOT break.
* Beware of impact to 'mkdirs.sh' when run with '-test'
* Review configure_new_servers.sh so it doesn't set SDP_* counters.
For the original 2007 pre-replication era of SDP, idea of having the
managed p4d data set be aware of the SDP version made sense; back
then the guidance was to version the SDP along with the customer's
data. In modern times, this concept is obsolete. The SDP can manage
multiple p4d data sets (aka SDP instances) on a given machine, but
those data sets are extended via replication and proxies to many
machines. The SDP version is bound to the machine, not the data set
it manages. In fact the SDP can be different on different machines
with the same data set.