nfs_clrpcops.c: NFSM_DISSECT() reply for each dir separately

Without this patch, the entire reply for all directories in
the NFSv4 mount path are parsed at once. This could cause
problems for mount paths with many directories in the path.

This patch fixes the problem by parsing each directory
reply in a loop.

Spotted while fixing other cases that could do large
NFSM_DISSECT() sizes.

(cherry picked from commit 9d13c87afdb35c0014aa6f43c5652e946c18b756)