BACKPORT: Smack: Correctly remove SMACK64TRANSMUTE attribute

BACKPORT: Smack: Correctly remove SMACK64TRANSMUTE attribute

Sam Henderson points out that removing the SMACK64TRANSMUTE
attribute from a directory does not result in the directory
transmuting. This is because the inode flag indicating that
the directory is transmuting isn't cleared. The fix is a tad
less than trivial because smk_task and smk_mmap should have
been broken out, too.

Targeted for git://git.gitorious.org/smack-next/kernel.git

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
(cherry-picked from upstream f59bdfba3e2b0ba5182f23d96101d106f18132ca)