Smack: Correctly remove SMACK64TRANSMUTE attribute

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

Change-Id: Iae25080bfd0ec247391c997a59f3e2327423e33d
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Rafal Krypa <r.krypa@samsung.com>