bhyve: workaround for the lack of UTC clock on ARM64

bhyve: workaround for the lack of UTC clock on ARM64

Currently, bhyve does not support UTC clock offset on ARM64.
However, when <clock offset= > is not specified in the domain XML,
UTC offset is used by default. That results in an incorrect
configuration for the bhyve ARM64 guests by default.

Workaround is to extend bhyveDomainDefPostParse() to fall back
to the LOCALTIME clock offset when UTC clock offset is not
supported by bhyve.

Signed-off-by: Roman Bogorodskiy <bogorodskiy@gmail.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>