No point in rewind() mtab in zfs_unshare_proto(). We're not really

reading the file, but instead use libzfs_mnttab_find() which does
the nessesary freopen() for us.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1498

lib/libzfs/libzfs_mount.c

@@ -877,7 +877,6 @@ zfs_unshare_proto(zfs_handle_t *zhp, const char *mountpoint,
 	char *mntpt = NULL;
 
 	/* check to see if need to unmount the filesystem */
-	rewind(zhp->zfs_hdl->libzfs_mnttab);
 	if (mountpoint != NULL)
 		mountpoint = mntpt = zfs_strdup(hdl, mountpoint);