src/rrd_fetch.c: Use "rrdc_fetch" if daemon is available.

src/rrd_fetch.c: Use "rrdc_fetch" if daemon is available.
Instead of flushing the file via the connection to the daemon and then
accessing it directly, use the "FETCH" command to access the file via
the RRDCacheD. This removes ambiguities with absolute and relative paths
and makes it possible to read data from files that are not available
locally. -- Florian

git-svn-id: svn://svn.oetiker.ch/rrdtool/trunk/program@2060 a5681a0c-68f1-0310-ab6d-d61299d08faa