[ONOS-YMS-TEST] 'space' is missing in the REST response string before 'is'

Issue:

1) 'space' is missing in the response body string before 'is'. Should be 'xyz is' instead of 'xyzis'
2) the string should not contain the ending \"

— POST ----
http://127.0.0.1:8181/onos/restconf/data/simple-rpc
{
"xyz" :{ }
}
— response —

{ "code": 500, "message": "Requested xyzis not child in simple-rpc in 0 at 0 in null\"" }

Confirmed by: Sonu