tests: Add new test f_rehash_dir

Add a new test which tests to make sure e2fsck -D works correctly.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

tests/f_rehash_dir/expect.1

@@ -0,0 +1,10 @@
+Pass 1: Checking inodes, blocks, and sizes
+Pass 2: Checking directory structure
+Pass 3: Checking directory connectivity
+Pass 3A: Optimizing directories
+Pass 4: Checking reference counts
+Pass 5: Checking group summary information
+
+test_filesys: ***** FILE SYSTEM WAS MODIFIED *****
+test_filesys: 105/2048 files (2.9% non-contiguous), 336/512 blocks
+Exit status is 1

tests/f_rehash_dir/expect.2

@@ -0,0 +1,7 @@
+Pass 1: Checking inodes, blocks, and sizes
+Pass 2: Checking directory structure
+Pass 3: Checking directory connectivity
+Pass 4: Checking reference counts
+Pass 5: Checking group summary information
+test_filesys: 105/2048 files (3.8% non-contiguous), 336/512 blocks
+Exit status is 0

tests/f_rehash_dir/script

@@ -0,0 +1,3 @@
+FSCK_OPT=-yfD
+
+. $cmd_dir/run_e2fsck