denoise tests/t_lpback.sh

denoise tests/t_lpback.sh

Introduce V=<nn> levels to t_lpback.sh self test

 V=0  - do not print any output at all
 V=1  - print intro line, summary at end, and "FAIL"+Log for failing tests
 V=99 - print everything + summary

code-wise, introduce test_start() / test_end() functions which do
the $? check as well, so the actual testing code is streamlined.

v2:
  replace indent tabs with spaces
  change [ $V == 1 ] expression to [ $V = 1 ] (POSIXly correct)

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20221004131403.95597-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25332.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>