Fix for CVLFAB-672
"Launcher does not call deleteMassiveJobIfNecessary() when the user
clicks the cancel button on the progress dialog"

In reality the deleteMassiveJobIfNecessary code is not used anymore,
and the code for canceling the job had a typo:

    event.loginprocess.stopCmd.format(**event.loginprocess.jobParams)

should have been

    event.loginprocess.siteConfig.stopCmd.format(**event.loginprocess.jobParams)

Due to the try/except block that quietly caught all exceptions, the log had no
details about what really went wrong. So I've added some more logging as well.
Removing unused code deleteMassiveJobIfNecessary().