test: use mntent in util/opal_path_nfs

[ggouaillardet]

Refs #4167

Signed-off-by: Gilles Gouaillardet gilles@rist.or.jp

[bwbarrett]

Two things about this patch. First, it doesn't actually fix the problem (see #4176) for the base indexing problem and how it should be fixed. Second, I'm not sure it's actually the right thing to test. We're now testing that the data returned from the unit test version of opal_path_nfs() and the library version of opal_path_nfs() return the same data, because they gather data essentially the same way. The "nice" thing about the mount method is that it's two totally different ways of collecting the data. The source of the data wasn't the problem; it was just a simple array bounds problem.

[ggouaillardet]

thanks for correction, i will close this PR then.