gbproxy: Use "(nsei << 16) | bvci" as rate_ctr_group index

As we now have gbproxy_bvc on both the SGSN and the BSS side
with the same BVCI, using the BVCI alone will no longer render
unique indexes.

Related: OS#4472
Change-Id: I13f3c9e69562a56ad7d3742fdeb2ba48f134fdaa
1 file changed