Bug fix: shared buffer between connection handlers.

TransportPacket was shared between server connections, leading to corruption.

Change-Id: Iaf06e6f6af27d69fce9731c5e90063119509ae1d
Reviewed-on: http://review.couchbase.org/41216
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>