Enable automated UI tests for starting dev mode in a container.

[mrglavas]

Container testing is disabled on all platforms (restricted to Linux when it was previously enabled) and based on our earlier investigations seems like that will continue to be a limitation for Windows/Mac unless the Liberty Maven/Gradle plugins become more flexible with timeouts and also address the issue(s) discussed here: #564. The goal is for the automated tests to run on all platforms, but at a minimum we should find a way to restore coverage on Linux. See #642 for more discussion about these tests.