qemu: Set always-on migration caps in ParamsCheck

qemu: Set always-on migration caps in ParamsCheck

Some migration capabilities are always enabled if QEMU supports them. We
can just drop the explicit code for them and let
qemuMigrationParamsCheck automatically set such capabilities.

QEMU_MONITOR_MIGRATION_CAPS_EVENTS would normally be one of the always
on features, but it is the only feature we want to enable even for other
jobs which internally use migration (such as save and snapshot). Hence
this capability is set very early after libvirtd connects to QEMU
monitor.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>