change tests that use complete() TMO for successful runs

Some tests await the completion TMO before checking for results. This can yield intermittent failures when running on loaded systems and generally doesn't play well with automatic bumping of TMO values when edgent.build.ci=true.

Most of the time the tests can define actual completion-conditions.

Being done as part of PR-309:
File connector: https://github.com/apache/incubator-edgent/pull/309/commits/e231c41ac38ede13d9cdc20473f09e8ea402e323
JDBC connector: https://github.com/apache/incubator-edgent/pull/309/commits/b7897e595072e2c4ae6a084a1a356018c2e5cb44
Command connector: https://github.com/apache/incubator-edgent/pull/309/commits/719fe6d8bf787e16cff01c49d86b2ae281437cc5
Websocket connector: https://github.com/apache/incubator-edgent/pull/309/commits/a6db4b8f9d2d49ba62f815c51fb4fd1cd3edc9b1
MQTT connector: https://github.com/apache/incubator-edgent/pull/309/commits/786d934f0837d387e2b97043a68cc56cc793608e