core: [Fix] Add host hotplug support checks

It is necessary to check the host (and OS) hotplug support of
vnic, disk and disk snapshot.

Change-Id: I8e4c8409c0de4ff1c959d27b54e793a31654326c
Signed-off-by: Gustavo Pedrosa <gustavo.pedrosa@eldorado.org.br>