Properly initialize back reference in connection copy

Change-Id: I2c4ff9827b13dd001bb54410bcbcad48714d8730
Reviewed-on: http://review.couchbase.org/35380
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>