I recently re-wrote cmd_test() to add new features. Add a bunch of unit-
tests to make sure I didn't break anything.

Suggested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>

"env default -f" doesn't work any more; replace it with
"env default -f -a". This avoids the following when running the ut
command:

do_ut_cmd: Testing commands
env - environment handling commands

Usage:
env default [-f] -a - [forcibly] reset default environment
...

Signed-off-by: Stephen Warren <swarren@nvidia.com>

Signed-off-by: Wolfgang Denk <wd@denx.de>
[trini: Fixup common/cmd_io.c]
Signed-off-by: Tom Rini <trini@ti.com>

Since run_command() and run_command_list() are important and a little
confusing, add some basic tests to check that the behaviour is correct.

Note: I am not sure that this should be committed, nor where it should go
in the source tree. Comments welcome.

To run the unit tests use the ut_cmd command available in sandbox:

make sandbox_config
make
./u-boot -c ut_cmd

(To test both hush and built-in parsers, you need to manually change
CONFIG_SYS_HUSH_PARSER in include/configs/sandbox.h and build/run again)

Signed-off-by: Simon Glass <sjg@chromium.org>