health_protocol: Fixing ECONNRESET handling

When running under a huge load, I had the following trace :
Exception happened during processing of request from ('10.77.7.35', 34010)
Traceback (most recent call last):
  File "/usr/lib/python2.7/SocketServer.py", line 593, in process_request_thread
    self.finish_request(request, client_address)
  File "/usr/lib/python2.7/SocketServer.py", line 334, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/usr/lib/python2.7/SocketServer.py", line 649, in __init__
    self.handle()
  File "./health-server.py", line 104, in handle
    msg = HP.recv_hm_message(socket_list[self.client_address])
  File "/srv/edeploy/src/health_protocol.py", line 77, in recv_hm_message
    if errno in [errno.ECONNRESET, errno.EBADF]:
AttributeError: 'int' object has no attribute 'ECONNRESET'

The code was incorrect at handling the errno. It shall come from the errno import not for the exception.
Adding more cases of disconnection too.