Allow XBZRLE decoding without enabling the capability
Before this fix we couldn't load a guest from
XBZRLE compressed file.
For example:
The user activated the XBZRLE capability
The user run migrate -d "exec:gzip -c > vm.gz"
The user won't be able to load vm.gz and get an error.
Signed-off-by: Orit Wasserman <owasserm@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>