Please add NFS support

[amschuma]

I'm trying out fsperf after LSF, and I'm getting this traceback when I try to use it for NFS:

Traceback (most recent call last):
File "/home/anna/fsperf/src/PerfTest.py", line 34, in run
self.commit_stats = utils.collect_commit_stats(self.dev)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/anna/fsperf/src/utils.py", line 445, in collect_commit_stats
fsid = get_fsid(device)
^^^^^^^^^^^^^^^^
File "/home/anna/fsperf/src/utils.py", line 407, in get_fsid
return subprocess.check_output(cmd, text=True).strip()
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.11/subprocess.py", line 466, in check_output
return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.11/subprocess.py", line 571, in run
raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['blkid', '-s', 'UUID', '-o', 'value', 'None']' returned non-zero exit status 2.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/anna/fsperf/src/fsperf.py", line 157, in
run_test(args, session, config, section, run_purpose, t)
File "/home/anna/fsperf/src/fsperf.py", line 46, in run_test
test.run(run, config, section, "results")
File "/home/anna/fsperf/src/PerfTest.py", line 29, in run
with self.test_context(config, section):
File "/usr/lib/python3.11/contextlib.py", line 589, in exit
raise exc_details[1]
File "/usr/lib/python3.11/contextlib.py", line 574, in exit
if cb(*exc_details):
^^^^^^^^^^^^^^^^
File "/home/anna/fsperf/src/utils.py", line 193, in exit
self.umount()
File "/home/anna/fsperf/src/utils.py", line 174, in umount
if self.is_on_block_device():
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/anna/fsperf/src/utils.py", line 199, in is_on_block_device
st_mode = os.stat(self.device).st_mode
^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: 'server:/srv/xfs/test/anna/nfsv41tcp'

I would be 100% okay with adding a flag to my local.cfg so it does the right thing if that's easiest