tests: Suppress xtfsutil output in ronly_replication_add_delete_replica.sh...

tests: Suppress xtfsutil output in ronly_replication_add_delete_replica.sh test as the failure msg actually means success to the test.

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@2748 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534