Get libgit2 sources from LHCb repository
With the recent switch of EOSWEB from SLC5 to CentOS7, HTTP requests to http://lhcb-rpm.web.cern.ch get redirected to https://lhcb-rpm.web.cern.ch and the version of TLS used is not understood by SLC5, so I changed the source URL for libgit2 to http://lhcb-repository.web.cern.ch
Closes lhcb-core/nightlies-jenkins-scripts#7 (closed)
This is practically a backport of !2330 (merged), but it was not felt as needed because we were already using a CERN server.
Edited by Marco Clemencic