SpawnTestEnvironment for external database cannot be used with SSH executor

[tomuben]

When using the luigi task SpawnTestEnvironment with an external database, the returned EnvironmentInfo object does not contain all necessary values to use later the SshExecFactory/SshExecutor. e.g. test_environment_info.database_info.user is missing.

Acceptance Criteria

1. Task SpawnTestEnvironment accepts additional parameters, e.g. ssh_user, ssh_public_keyfile
2. The task or subsequent api layers add this parameter to the instance of class lib.data.environment_info.EnvironmentInfo
3. Create a test for this scenario