testsuite: Fix colorize

testsuite: Fix colorize

bash and dash require for escape sequence to use 'echo -e' or printf
(but working on zsh). Choosing printf as it's implementation is IMHO
more portable than echo implementations.
dash also require to use \033[0; as escape sequence instead of \e[0;

NOTE: \e[0; kept in lib/color.c as it's not problematic for C code
(working when run ip on various shells).

Fixes: 7e2f71b4 ("testsuite: colorize test result output")
Signed-off-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>