gocbcore incorrectly tries to parse the collection id for 'cmdStat/0x10'

When gocbcore reads a packet using 'ReadPacket - gocbcore/memdconn.go:232' it incorrectly tries to read the collection id for the DCP command 'cmdStat/0x10'.

Expected behaviour:
The backup/restore tooling is using 'StatsEx - gocbcore/agentops_crud.go:1007' to get the current high/purge sequence numbers on a per vbucket basis; the expected keys in the single server stats map defined in 'gocbcore/agentops_crud.go:996' should be prefixed with 'vb_<vbucket_id>'.

Actual behaviour:
The keys are prefixed with 'b_<vbucket_id>' .