BibSched: parse_runtime_limit() fix

* Fixes bug in parse_runtime_limit which would give a limit
  range in the past, when expected returned ranges should always
  either contain the current time or being in the future.
  (closes #1432)

Co-authored-by: Samuele Kaplun <samuele.kaplun@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
WebSession: unit vs regression test suite cleanup

* The current webuser unit tests depends on the installed Atlantis
  Demo site and need therefore be moved into the corresponding
  regression test suite.

Co-authored-by: Tibor Simko <tibor.simko@cern.ch>