LU-10199 utils: strip // from fid2path

LU-10199 utils: strip // from fid2path

There are a few ways to get a path with a // back from
fid2path, make sure we strip them all out

Signed-off-by: Ben Evans <bevans@cray.com>
Change-Id: I30591585ccf62e4d793ee658d2772ce1db242034
Reviewed-on: https://review.whamcloud.com/30078
Tested-by: Jenkins
Reviewed-by: Steve Guminski <stephenx.guminski@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>