core: Require a lock fo VdsNonReposonding treatment

this is an addition for 1026811 work

Change-Id: I709ea327b5f66ab5a676e5e13776752ca650d4be
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1026811
Signed-off-by: Roy Golan <rgolan@redhat.com>