Validation function doesn't check all ouptut options before failing

[hannahbnelson]

The validation of the lobster configuration seems to completely fail after checking one output option instead of also checking other output options.

For example, because of #685, validating an XrootD path for the output fails.
In simple.py, using direct file access as the first option and then including xrootd as the second options passes validation because validating the workflow using direct file access succeeds.
The successful setup is:

    output=[
        "file:///cms/cephfs/data/store/user/$USER/lobster_test/" + version,
        "root://hactar01.crc.nd.edu//store/user/$USER/lobster_test/"+version,
    ]

But, changing the order of the output to

    output=[
        "root://hactar01.crc.nd.edu//store/user/$USER/lobster_test/"+version,
         "file:///cms/cephfs/data/store/user/$USER/lobster_test/" + version,
    ]

fails with the following error message:

(lobster-python3) [hnelson2@glados examples]$ lobster process simple.py
usage: lobster [-h] [--verbose] [--quiet] {configuration,configure,plot,process,status,terminate,validate} ... {configfile,workdir}
lobster: error: configuration 'simple.py' failed validation: failed to create stageout directory for 'ttH'

So, it appears that when the XrootD validation fails, lobster does not try the next provided option for output for the validation check.