requestor: handle the case of socket error in login method
requestor: handle the case of socket error in login method

cloudmonkey would break if mgmt server is not running instead of handling the
case of socket error, connection refused. The fix adds a try catch block on the
login by username/password mechanism.

Signed-off-by: Rohit Yadav <902b9eb5dd62819678163bd5e00fbf0cbc7c264b@shapeblue.com>

Interoute/cloudmonkey-interoute,apache/cloudstack-cloudmonkey,Interoute/cloudmonkey-interoute,remibergsma/cloudstack-cloudmonkey,remibergsma/cloudstack-cloudmonkey,apache/cloudstack-cloudmonkey