Crash in MCResponse.Receive

Seen in xdcr perf test on hot load phase. It is currently blocking MB-15433

panic: runtime error: slice bounds out of range
goroutine 4673 [running]:
github.com/couchbase/gomemcached.(*MCResponse).Receive(0xc229fe7ce0, 0x7f2482989b18, 0xc25312a1f8, 0xc23d0d8800, 0x18, 0x18, 0xcaad00, 0x0, 0x0)
/home/couchbase/jenkins/workspace/sherlock-unix/godeps/src/github.com/couchbase/gomemcached/mc_res.go:176 +0x825
github.com/couchbase/gomemcached/client.getResponse(0x7f2482989b18, 0xc25312a1f8, 0xc23d0d8800, 0x18, 0x18, 0xc229fe7ce0, 0x0, 0x0, 0x0)
/home/couchbase/jenkins/workspace/sherlock-unix/godeps/src/github.com/couchbase/gomemcached/client/transport.go:35 +0xe1
github.com/couchbase/gomemcached/client.(*Client).Receive(0xc23d0a1b00, 0xc2092f6d80, 0x0, 0x0)
/home/couchbase/jenkins/workspace/sherlock-unix/godeps/src/github.com/couchbase/gomemcached/client/mc.go:96 +0x8f
github.com/couchbase/goxdcr/parts.(*XmemNozzle).readFromClient(0xc208344c80, 0xc2092f6d80, 0x0, 0x0, 0x0, 0xcaad60)
/home/couchbase/jenkins/workspace/sherlock-unix/goproj/src/github.com/couchbase/goxdcr/parts/xmem_nozzle.go:1964 +0x396
github.com/couchbase/goxdcr/parts.func·004(0x1f4, 0xc24172e690, 0xc24172e700, 0xc239eef020, 0xc239eeeff0, 0xcb3dd0, 0x0, 0x0, 0xc20c92bb40, 0xc2081ee950, ...)
/home/couchbase/jenkins/workspace/sherlock-unix/goproj/src/github.com/couchbase/goxdcr/parts/xmem_nozzle.go:1200 +0x23b
created by github.com/couchbase/goxdcr/parts.(*XmemNozzle).batchGetMeta
/home/couchbase/jenkins/workspace/sherlock-unix/goproj/src/github.com/couchbase/goxdcr/parts/xmem_nozzle.go:1244 +0x44c