CHE-3844: Show 'Add terminal button' in the machine node when WsAgent started.

[AndrienkoAleksandr]

What does this PR do?

Show 'Add terminal button' in the machine node when WsAgent started. Earlier We shown this button when machine had got status "running", but on this phase start IDE terminal agent was not installed yet.

What issues does this PR fix or reference?

#3844

Changelog

Show 'Add terminal button' in the machine node when WsAgent started.

Release Notes

Show 'Add terminal button' in the machine node when WsAgent started.

Docs PR

Not needed, this is bug fix.

[vparfonov]

But if machine status is "RUNNING" terminal agent should be ready, no?

[codenvy-ci]

Build # 2284 - FAILED

Please check console output at https://ci.codenvycorp.com/job/che-pullrequests-build/2284/ to view the results.

[AndrienkoAleksandr]

@vparfonov About "But if machine status is "RUNNING" terminal agent should be ready, no?" it really was in the some previous version, but not in the current version server api. Look here: https://github.com/eclipse/che/blob/master/wsmaster/che-core-api-workspace/src/main/java/org/eclipse/che/api/workspace/server/WorkspaceRuntimes.java#L430
We first start machine and during this operation machine gets status "creation" -> then "running", and after machine is running we launch agents.

[AndrienkoAleksandr]

I was wrong about this pull request. We should show terminal add button when workspace is running:
#4618