EX-3658 pumount: correct path escaping

EX-3658 pumount: correct path escaping

Correct the test for whether a character needs escaping in
pu_str_escape2(). Add sanity-pumount 55f-g to verify.

Test-Parameters: trivial testlist=sanity-pumount clientextra_install_params="--packages pumount"
Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I248f56752b30836636734f43d16741511717709c
Reviewed-on: https://review.whamcloud.com/44759
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/44959
Tested-by: Andreas Dilger <adilger@whamcloud.com>