mon/PGMonitor: use post_paxos_update, not init, to refresh from osdmap

We do two things here:
 - make init an one-time unconditional init method, which is what the
   health service expects/needs.
 - switch PGMonitor::init to be post_paxos_update() which is called after
   the other services update, which is what PGMonitor really needs.

This is a new version of the fix originally in commit
a2fe013794 (and those around it).  That is,
this re-fixes a problem where osds do not see pg creates from their
subscribe due to map_pg_creates() not getting called.

Backport: cuttlefish
Signed-off-by: Sage Weil <sage@inktank.com>

src/mon/Monitor.cc

@@ -520,14 +520,14 @@ void Monitor::init_paxos()
   dout(10) << __func__ << dendl;
   paxos->init();
 
+  // init services
+  for (int i = 0; i < PAXOS_NUM; ++i) {
+    paxos_service[i]->init();
+  }
+
   // update paxos
   if (paxos->is_consistent()) {
     refresh_from_paxos(NULL);
-
-    // init services
-    for (int i = 0; i < PAXOS_NUM; ++i) {
-      paxos_service[i]->init();
-    }
   }
 }
 

src/mon/PGMonitor.cc

@@ -271,7 +271,7 @@ void PGMonitor::upgrade_format()
   propose_pending();
 }
 
-void PGMonitor::init()
+void PGMonitor::post_paxos_update()
 {
   if (mon->osdmon()->osdmap.get_epoch()) {
     map_pg_creates();

src/mon/PGMonitor.h

@@ -53,7 +53,7 @@ private:
   void create_initial();
   void update_from_paxos(bool *need_bootstrap);
   void upgrade_format();
-  void init();
+  void post_paxos_update();
   void handle_osd_timeouts();
   void create_pending();  // prepare a new pending
   // propose pending update to peers