Fix lvresize test on RHEL 5, by fixing guestfs_e2fsck_l.

The problem is that mkfs was making an ext2 filesystem,
which later we were checking with e4fsck.  e4fsck corrects
an "error" on the filesystem:
  /dev/VG/LV: Adding dirhash hint to filesystem.
e4fsck returns 1 (errors corrected) which we were interpreting
as an error return.