core:fix adding host from REST API

Fixing a regression resulted from commit
31cd7918c9c5eb5c2d6ddf5526b366fdb2d0f4bc (PM refactoring)

The regression caused a host added using cluster name to fail.

Change-Id: I527e79102ae7af5d2bb6703e20dd388677da30c2
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1176391
Signed-off-by: emesika <emesika@redhat.com>