* Feature #2681, to add a script in xCAT-test to get the performance baseline for node range operation.
* adopt review comments in PR#2916:
1, add the rst file for xcatperftest (#2681)
2, using /bin/bash as script executor
3, FILES in manpage should not be in the same line
4, minor adjustment if PERF_NOCREATE/PERF_DRYRUN is set
