Don't panic if we can both do conditional (IMS) and stream, prefer IMS, it is less work and less data to transmit.
Don't panic if we can both do conditional (IMS) and stream,
prefer IMS, it is less work and less data to transmit.

Fixes	#972

Thanks to:	Martin

wikimedia/operations-debs-varnish,wikimedia/operations-debs-varnish,ssm/pkg-varnish,ssm/pkg-varnish,wikimedia/operations-debs-varnish,ssm/pkg-varnish,wikimedia/operations-debs-varnish,ssm/pkg-varnish,wikimedia/operations-debs-varnish,ssm/pkg-varnish