Make some lbexec tests independent of the value of GAUDIAPPNAME

In some cases (in particular CMake builds with a super project) tests are run with an arbitrary value for the environment variable GAUDIAPPNAME.

I found two lbexec tests that assume GAUDIAPPNAME is set to LHCb, thus failing if it is not the case.

This MR changes the tests to work regardless of the value of GAUDIAPPNAME.

See gaudi/Gaudi#233 (closed) too.