Add extra_msg and server parameter to check_vm_connectivity

Now manager.check_public_network_connectivity just adds log ex_msg
and log console output based on check_vm_connectivity, and the same
helper name also exists in TestNetworkBasicOps, so this is to:
1. add extra_msg and server parameter to manager.check_vm_connectivity, so
   it can log extra_msg and log console output.
2. add server parameter to manager.ping_ip_address, so it can log console
   output for the specific server while not self.servers, because in its
   use cases only the server owning the ip address is needed for console output.
3. add underscore before TestNetworkBasicOps.check_public_network_connectivity
   because it is an internal helper, and replace its calling super's
   check_public_network_connectivity with calling self.check_vm_connectivity
4. remove manager.check_public_network_connectivity

Change-Id: Ibe8966cabbb2c9264640ba3f559a0146be588aa0
3 files changed