crush: fix crash from invalid 'take' argument

Verify that the 'take' argument is a valid device or bucket.
Otherwise ignore it (do not add the value to the working vector).

Reflects ceph.git commit 9324d0a1af61e1c234cc48e2175b4e6320fff8f4.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>