[bgpcfgd]: Don't use neighbor metadata in bgpmon sessions (sonic-net#…

…5506)

**- Why I did it**
BGP_MONITORS sessions don't have corresponding DEVICE_NEIGHBOR_METADATA CONFIG_DB entries in the minigraphs. Prevent bgpcfgd to wait on such entries for BGP_MONITORS sessions.

**- How I did it**
Set constructor argument to False that means - don't wait for device neighbors metadata info for BGP_MONITORS

**- How to verify it**
Build an image, write on your device, use a minigraph with BGP_MONITORS sessions. Check that sessions are populated in the config.

src/sonic-bgpcfgd/bgpcfgd

@@ -876,7 +876,7 @@ def main():
         ZebraSetSrc(common_objs, "STATE_DB", swsscommon.STATE_INTERFACE_TABLE_NAME),
         # Peer Managers
         BGPPeerMgrBase(common_objs, "CONFIG_DB", swsscommon.CFG_BGP_NEIGHBOR_TABLE_NAME, "general", True),
-        BGPPeerMgrBase(common_objs, "CONFIG_DB", "BGP_MONITORS", "monitors", True),
+        BGPPeerMgrBase(common_objs, "CONFIG_DB", "BGP_MONITORS", "monitors", False),
         BGPPeerMgrBase(common_objs, "CONFIG_DB", "BGP_PEER_RANGE", "dynamic", False),
     ]
     runner = Runner()