[FIXED JENKINS-23020 JENKINS-23942] Convert the queue's cancel shutdown to POST

Both 0 and 1 are used to indicate some kind of success (the latter when Jenkins doesn't need to be started because it was already running), so we need to return 2.

java.lang.NullPointerException
	at hudson.model.User.idStrategy(User.java:140)
	at hudson.model.User.getOrCreate(User.java:373)
	at hudson.model.User.get(User.java:366)
	at hudson.model.User.get(User.java:331)
	at hudson.model.User.get(User.java:441)
	at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.getAuthentication(CpsFlowExecution.java:614)
	at org.jenkinsci.plugins.workflow.cps.CpsVmThread.run(CpsVmThread.java:20)

Conflicts:
	.idea/encodings.xml
	core/pom.xml
	pom.xml
	test/src/test/java/hudson/tasks/junit/CaseResultTest.java

Integrated the change

Add getFieldOrder() methods.

Add getFieldOrder() methods to classes which extend com.sun.jna.Structure,
for compatibility with newer versions of JNA.  [JENKINS-24521]

Bumping up dependencies to 1.3.1, with extra precaution to make
DiskFileItem non-serializable

init script: don't try to run on Java 5

Use copytruncate consistent with .deb packaging

also requires no signalling of the process and less risk of (ironically) lost logs which postrotate attempts to address.

The primary change is that the thread name update code now lives in a
filter instead of 'Stapler' servlet, so it happens a lot earlier.

Also sending the exception to the log, which is where plugin developers expect to see it.
(This is also necessary for the exception to be visible say from configRoundtrip in a functional test.
Otherwise you just see a FailingHttpStatusCodeException due to the 400 error code, with no details.)
Might actually suffice to just throw a ServletException wrapping the exception up the chain,
letting Stapler or the container handle it, but this change is more conservative.

sendError(Exception…) should set the exception attribute on the response, since error.jelly handles this nicely.

(cherry picked from commit 261f4053)

(cherry picked from commit facfc178)