adde file /etc/rucio.conf.d/ca.crt in spec

This file was missing in the spec, thus building an rpm with mock failed with:

2-May-2013 10:15:07 	DEBUG: Processing files: dmlite-plugins-rucio-debuginfo-0.1.0-1.el6.x86_64
02-May-2013 10:15:07 	DEBUG: Checking for unpackaged file(s): /usr/lib/rpm/check-files /builddir/build/BUILDROOT/dmlite-plugins-rucio-0.1.0-1.el6.x86_64
02-May-2013 10:15:07 	DEBUG: RPM build errors:
02-May-2013 10:15:07 	DEBUG: error: Installed (but unpackaged) file(s) found:
02-May-2013 10:15:07 	DEBUG:    /etc/rucio.conf.d/ca.crt
02-May-2013 10:15:07 	DEBUG:     Installed (but unpackaged) file(s) found:
02-May-2013 10:15:07 	DEBUG:    /etc/rucio.conf.d/ca.crt