PRESKIP jobs are not noop jobs #2966

Account for the following bug that tripped up tests by wenger and in
NMI:

	When I run the job_dagman_recovery_preskip.run test with the latest
	version, I fail an assertion:

	  ERROR "Assertion ERROR on (isNoop == node->GetNoop())" at line 1325 in file
	  /scratch/wenger/condor_build/git5/CONDOR_SRC/src/condor_dagman/dag.cpp

	Also, I think the test script should delete the lock file
	(job_dagman_recovery_preskip.dag.lock) if it exists, just in case we
	have one hanging around for some reason.