core: fix conflicting getter definitions

For several boolean fields in RunVmParams we have both "isX" & "getX"
getters, thus json produce: IllegalArgumentException: Conflicting
getter definitions for property.

The solution is to remove the "isX" getters which should be used only
for primitive boolean fields.

Change-Id: I37b5e286c21814e757e6369ef9b2a642ac0c621d
Signed-off-by: Arik Hadas <ahadas@redhat.com>