MB-12475: Add better error message in cbepctl for timeout errors

A timeout weeror usually occurs when the user enters the wrong
ip address or port number. This changes adds an error message
to tell the user to double check these values.

Change-Id: Ifbfb7f74a1c354720530faede3b86b26fa4592a5
Reviewed-on: http://review.couchbase.org/43148
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>