Fix for NFSv3 mounting of descendant dirs in exports.
Mounting /a/b/c when /a/b is exported would throw a permission denied error.
This was due to a strcmp over the wrong string length.

Also, we were checking the intersection point in the export path instead
of the mount path. Thus, we weren't properly checking if the mount path's
last dir name was an extension of the export path's last dir name.

Signed-off-by: Jeremy Bongio <jbongio@us.ibm.com>