memcached: better error messaging

memcached: better error messaging

MemcachedClient output a generic error message: "Error parsing memcached
response\n" whenever it is not able to read from the socket. It is also
lacking the remote peer it is reading from.

This patch add a new message when fgets( <socket> ) return false, which
means we could not read from the file pointer. It also get the stream
remote name for debugging purposes.

Change-Id: I9b8a25a03af0d730aa3b4830a44b1ea739343274