s3:wscript: enable Spotlight by default

s3:wscript: enable Spotlight by default

Now that we have a no-op backend that is always available, we can compile mdssvc
by default.

The new behaviour is:

option not used       Default: build mdsvc with available backends
                      from autodetection
--disable-spotlight   Do not build mdssvc
--enable-spotlight    Build mdssvc and require a real backend
		      (currently Tracker, in the future also Elasticsearch)

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>