info: remove emi.version from non-EMI dCache releases

dCache v2.7 and later are not part of any EMI release, therefore we
should not publish an EMI version for these releases.

For v2.6 the situation is more complicated, since the version is
released both through EMI and dcache.org.  Future patches may make this
distinction, allowing non-EMI releases to omit publishing any EMI
version.

Target: master
Request: 2.8
Request: 2.7
Patch: http://rb.dcache.org/r/6854/
Acked-by: Gerd Behrmann