Changes

ttcn3: remove /root/projects/git symlink

Remove leftover from old TTCN-3 build scripts, before refactoring ttcn3
Dockerfiles. This line has already been removed in 357ec806 from 2017 for
ggsn-test.

In osmo-ttcn3-hacks.git, this is only referenced in the obsolete
bin/install.script (looks like we could remove that, together with the
rest of the bin dir?).

Related: OS#5017
Change-Id: Id23e7fae58ba246916a38aa0a10035d4f67f7588

ttcn3: move initial clone to debian-stretch-titan

Clone the osmo-ttcn3-hacks and all dependency repositories less often by
moving related commands to the shared debian-stretch-titan image.

Remove the 'git checkout -f -B master origin/master' line, because the
master branch is checked out by default.

While at it, move the shared "git config" commands too, and move them
before cloning the repositories, so they don't run again whenever the
deps change (logic to invalidate the cache if deps change will be added
in the next patch).

Related: OS#5017
Change-Id: I2bb142dce061eba4b6a828c4e435510e309989fd

debian-stretch-titan: update deps on change

After the initial clone of osmo-ttcn3-hacks and deps, let docker
download deps/Makefile to invalidate the cache if the file changed.

Run "git pull" and "make deps" afterwards, but only if the Makefile is
different. The "if" saves time in the initial build of the image, it
avoids the "git fetch" on every dependency repository during "make deps".

Related: OS#5017
Change-Id: I56673312cfb23375d67900016aaac1931f677275

ttcn3: move prepare code to shared script

Move the git fetch/checkout code and make call to build the testsuite,
to debian-stretch-titan/ttcn3-docker-prepare.sh. In the next patch, I
will extend the script to update deps right before building too (e.g.
because OSMO_TTCN3_BRANCH changed).

Related: OS#5017
Change-Id: I4b5bedf058dc527e821f9b7204c632820e671af9

debian-stretch-titan: prepare: run 'make deps'

Run 'make deps' in ttcn3-docker-prepare.sh, if needed.

Related: OS#5017
Change-Id: I9085203b27d310b63a035fd71f7c2a78d02710d4

debian-stretch-titan: prepare: start/stop links

Create symlinks to ttcn3-*-start.sh and ttcn3-*-stop.sh in the
prepare.sh script instead of in each of the ttcn3 Dockerfiles.

Related: OS#5017
Change-Id: I634cf71cff7936efe6e0461d21dc1119de922ada

ttcn3: move shared run code to script

While I'm at it with tidying up the Dockerfiles, create a
ttcn3-docker-run.sh with shared run code.

Related: OS#5017
Change-Id: Id90769707158f0488eca2313c57b99ea7a4a27c8

ttcn3-{fr,gbproxy}-test: use ttcn3-docker-run too

Move the shared pipework script to the base image, and call it in
ttcn3-docker-run.sh if WAIT_FOR_NETDEV is set. Use ttcn3-docker-run.sh
as entrypoint in both Dockerfiles and remove the custom entrypoint
scripts (which are the same as ttcn3-docker-run.sh now).

Related: OS#5017
Change-Id: I2889abe94ed522a205890e5cb39e09cbebfbd820