mon: Remove global version code introduced around bobtail's release

mon: Remove global version code introduced around bobtail's release

This patch reverts most of the global version (gv) related patches that
were introduced around bobtail's release as a prelude to the single-paxos
patches.

The gv infrastructure allowed us to gather version information on the
monitors, essential to the move to a single-paxos implementation on
existing clusters -- this means that for an existing cluster to upgrade
to the a single-paxos monitor, it will first have to be upgraded to a
version prior to this patch.  This patch strips the monitor subsystem of
all the gv-related code that is of no use for upcoming versions.

Furthermore, from this patch onwards until all single-paxos patches
are merged, ceph-mon won't work as expected, and may not compile at some
point in the git history.

These patches are not retro-compatible, and the monitors are not expected
to work with earlier versions.

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>