Investigate removing use of the Attach API

[Azquelt]

Issue Overview

We use the attach API to get hold of the JMX URL. However, this URL is also written to a file by the localConnector-1.0 feature. We might be able to avoid using the attach API altogether which would simplify the code somewhat.

I think we also use the Attach API to see if the server is already running, so we'd also have to find another way of doing that.

localConnector docs: https://www.ibm.com/support/knowledgecenter/en/SSEQTP_liberty/com.ibm.websphere.wlp.doc/ae/twlp_admin_localconnector.html