httpserver: register /env API

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
httpserver: tests: do not ignore request failures

Currently curl() would return '' in case of HTTP or network errors.

Becasuse of this the test 'test_env' was passing even though the
server returned 404 for GET /env/test-param?val=TEST request.

Other test cases could have also incorrectly pass because of this.

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
mgmt: update to latest

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>