invenio-backup-site: respect configured user

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
invenio-retest-demo-site: DB prefix in file names

* Uses database name as the prefix in output file names.
  Useful not to mix output files from different virtual
  environments (e.g. inveniomaint11-retest-demo-site*,
  inveniomaster-retest-demo-site*).

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
invenio-retest-demo-site: fully skip web tests

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>