tracker-miner-rss: Only change mfo:updatedTime if a feed is added
tracker-miner-rss: Only change mfo:updatedTime if a feed is added

Also used proper GCancellable for all SPARQL calls

hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker