qemu: migration: Use correct flag constant for enabling storage migration

qemu: migration: Use correct flag constant for enabling storage migration

The 'storageMigration' flag is supposed to be true if storage migration
is requested, which is based on VIR_MIGRATE_NON_SHARED_DISK or
VIR_MIGRATE_NON_SHARED_INC flags. The assignment to the variable used
QEMU_MONITOR_MIGRATE_NON_SHARED_INC (0x04) instead of
VIR_MIGRATE_NON_SHARED_INC (0x80), caused libvirtd to skip the actual
copy of data.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1978526
Fixes: da69f4b2084bff140238e450e264d6036ebef898
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>