backend: logging change in VdsManager.

Users do not care about called method name but
about what it does.

Change-Id: I25dc387dfa6b9499115bcd811c9bffb45b09e996
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1066693
Signed-off-by: Mooli Tayer <mtayer@redhat.com>