gluster: Remove non-readable characters in gluster volume warning messages

Remove <br/> characters and updated with \n in UIConstants.java file for
distributed replicate volume warning messages.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1021982
Change-Id: I1cc9a1fc33fdc28abb930f8fefbb65432436919a
Signed-off-by: Timothy Asir <tjeyasin@redhat.com>