Revert "block: export blk_{get,put}_queue()"

This reverts commit ea0770b8

.

We reverted the commit "Fix oops caused by queue refcounting failure"
that needed this blk_{get,put}_queue() export, thus we don't need it for
now.

This revert is being tracked in bug 802986.

Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>