test: validate test names in non interactive mode

test: validate test names in non interactive mode

When passing in test names to run via either the DPDK_TEST environment
variable or via extra argv parameters, the checks run on those commands
can miss valid commands that are registered with the cmdline library in
the initial context used to set it up. This is seen in the fact that the
"dump_*" set of commands are not callable via argv parameters, but can
be called manually.

To fix this, just use the commandline library to validate each command
before executing it, stopping execution when an error is encountered.
This also has the benefit of not having the test binary drop to
interactive mode if all commandline parameters given are invalid.

Bugzilla ID: 1002
Fixes: 9b848774a5dc ("test: use env variable to run tests")
Fixes: ace2f054ed43 ("test: take test names from command line")

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>