Jetty 9.3.3+ tries to write start properties file to jetty.base dir

[ato]

This change conflicts with our model of a read-only jetty base directory:
jetty/jetty.project@837a36e

A second commit makes the properties file path configurable
jetty/jetty.project@aca2aa5

So probably our best bet is to specify a path in /var/run/. Presumably older versions of Jetty error when given that argument though so we'll have to gate it on jetty version somehow.

Workarounds for now either:

• Use a version of Jetty prior to this change
• Manually make jetty base directory writable by the user the application is running as.