ext4 crypto: set up encryption info for new inodes in ext4_inherit_context()

Set up the encryption information for newly created inodes immediately
after they inherit their encryption context from their parent
directories.

Change-Id: Ie2a48cde918eaf8ad978a8a698de24627b363955
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Theodore Ts'o <tytso@google.com>