ceph-monstore-tool: use a large enough paxos/{first,last}_committed

ceph-monstore-tool: use a large enough paxos/{first,last}_committed

so the rebuild paxos transaction won't be overwritten by the ones
created before recovery completes.

when the quorum is recovering, the leader will collect the paxos
transactions from peons. if the quorum accept the proposal for setting
the fingerprint, the peon will update the monitor with the paxos
transaction with a newer "last_committed" than the one created using
update_paxos() in ceph_monstore_tool.cc. the latter "last_committed" is
always 0.

so, to avoid this extra paxos proposal obsoleting the "rebuilding" paxos
transaction, we use a large enough number for {first,last}_committed.

Fixes: http://tracker.ceph.com/issues/38219
Signed-off-by: Kefu Chai <kchai@redhat.com>
(cherry picked from commit 5475ef7843ab4021eddee60c2789b81d616383e9)