Also JIT non-startup methods in zygote.

Noticed this while looking at systraces - the original code I've put
in was only adding startup methods.

Also don't create a JNI global reference for boot classpath classes which
will never get GCed.

Test: startup dialer, look at systrace
Bug: 119800099
Change-Id: I12c173a85f8a8bc393693432624c54d916161bf7