Cleanup conn_shrink

All that extra casting just makes the code hard to read.

Change-Id: I2ab8bd1599d26b7ce670c51d4ab06f7fbd0bf09f
Reviewed-on: http://review.couchbase.org/38066
Reviewed-by: Dave Rigby <daver@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>