Handle the case of multiple mounts with virt-sandbox-service.
Handle the case of multiple mounts with virt-sandbox-service.

Currently if you execute

   virt-sandbox-service create --mount=... --mount=...

Only the last mount gets added via the argparser, since the
arg is parsed as a scalar, not a list

Signed-off-by: Daniel P. Berrange <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

agx/libvirt-sandbox-debian,libvirt/libvirt-sandbox,agx/libvirt-sandbox-debian,gczarcinski/libvirt-sandbox,libvirt/libvirt-sandbox,gczarcinski/libvirt-sandbox,erenyagdiran/libvirt-sandbox,erenyagdiran/libvirt-sandbox,gczarcinski/libvirt-sandbox,agx/libvirt-sandbox-debian,gczarcinski/libvirt-sandbox,agx/libvirt-sandbox-debian,agx/libvirt-sandbox-debian,erenyagdiran/libvirt-sandbox,libvirt/libvirt-sandbox,gczarcinski/libvirt-sandbox,erenyagdiran/libvirt-sandbox,gczarcinski/libvirt-sandbox