fixup: ttcn3-tcpdump*.sh: Fix output of special chars

On ArchLinux /bin/sh is actually a symlink to bash, so bash is running
in limited mode and emulating the Bourne Shell.  The shell detection
logic added in [1] does not work correctly for me because the cmdline
would be 'sh' or '/bin/sh', not 'bash'.  This is what I am getting:

  \033[1;32m====== FooBar_Tests.TC_foo_bar pass ======\033[0m

Let's switch to printf, which does interpret the backslash escapes
as expected by default, regardless of the actual shell in use.

Also fix ttcn3-dumpcap-stop.sh, which was left untouched by [1].

Change-Id: Id28193a7ca00b5501a6852e5b4a5412fbaa5e063
Fixes: [1] bf45a5cff890a6103c68d76c1cf088c26ca9aa80
2 files changed