e2fsck: add test for ea_inode feature

e2fsck: add test for ea_inode feature

f_ea_inode test covers the following scenarios:

- a file that contains old Lustre-style valid ea_inode references
  in inode body and xattr block

- a file that contains new style valid ea_inode references in inode
  body and xattr block

- a file with an extended attribute that references an invalid inode
  number (e_value_inum > s_inodes_count)

- an ea entry with bad e_hash and points to an inode that does not
  have EA_INODE flag set

- an ea entry with bad e_hash but points to a valid ea_inode

- an ea entry with valid e_hash that points to an inode that is
  missing EA_INODE flag

Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>