ggsn: Disable GTP-U tx sequence number by default

GTP-U transmit sequence numbers are entirely optional and probably
don't serve any real purpose in real-world deployments.

While OsmoGGSN in userspace implements support for it, the kernel GTP-U
implementation doesn't.  This means a number of tests fail against
kernel GTP-U only for that reason.

Let's switch all tests to disable GTP-U sequence numbers, and only
enable it in one specific test.  This way, we can execute the tests
also against kernel GTP-U.

Related: OS#3215
Change-Id: I666f5276749ef6a1a4dc170a3b9a747f626f6b2c
1 file changed