Changes

ttcn3-bts-test: add env var to not run all configs

Make it possible to e.g. run only one of the generic/oml/hopping
configurations.

I made a version of this patch a few weeks ago for testing OS#6375,
and I'm submitting it now so I can add multiple configurations for
ttcn3-ggsn-test in the next patch with the same logic.

Change-Id: I1dce5e6aa4b5d67f9f8c96ced611ab2875c353c8

ttcn3-ggsn-test/jenkins: add functions for start ggsn/testsuite

Prepare to run start_ggsn and start_testsuite multiple times with
different configurations in a follow-up patch.

Related: OS#6096
Change-Id: I0754b0df5f1b0b162732c3db0797f65676553ab0

ttcn3-ggsn-test: move confgs to subdirs

Prepare to add variations of the configs: move them to subdirs, so we
don't cullter the main directory.

Related: OS#6096
Change-Id: I03a06f9f516922c47e3092ff7d7c2c68b0852c1b

ttcn3-ggsn-test: run with multiple configurations

The kernel ttcn3-ggsn-tests have been failing since the osmo-ggsn
config for kernel-gtp has been adjusted for v4v6 instead of v4 only.

This new configuration caused a regression with:
* linux kernel without Pablo's GTP IPv6 patches
* latest stable release of osmo-ggsn, which does not support IPv6

As the kernel patches aren't merged yet, this caused all tests to fail.

Avoid this by running the ttcn3-ggsn-test with multiple configurations:
* v4_only: one APN with v4
* v6_only: one APN with v6
* v4v6_only: one APN with v4v6
* all: multiple APNs with all of the above

With this change, the tests running in the v4_only configuration will
pass again with the stable versions of osmo-ggsn, libgtpnl and kernel.
And with new versions, most test in the other configurations will pass
too.

As discussed with Harald, this does not only split up the configuration
for osmo-ggsn with kernel gtp-u, but also with the userspace
implementation. The "all" config currently only works with the
userspace gtp implementation (OS#6106).

Related: OS#6096
Depends: osmo-ttcn3-hacks I6d94a8b18200fbb2119406827b74b83e912e3ecc
Fixes: e24442f9 ("ttcn3-ggsn-test: kernel-gtp: add ipv6")
Change-Id: Ia2fe0c3ed4ccf06e72fd258d085e4a79cecd5f26