switch to the LCG_93c

Thanks to @graemes we have now LCG_93c with root built with Davix support. This change is apparently minor enough that we don't need a new TDAQ- and DQM-Common versions (@akazarov ?). I managed to build the athena master branch against the LCG_93c installation on /cvmfs/sft.cern.ch/ and the current versions dqm-common-01-07-00 and tdaq-common-02-07-00. The q221 test ran successful, q431 still running.

This addresses the bugs https://its.cern.ch/jira/browse/ATEAM-467 and https://sft.its.cern.ch/jira/browse/SPI-1078

AFAIK, RPMs for LCG_93c are still being worked on.