[SECURITY-218] - Functional tests for CLI

[SECURITY-218] Blackbox test

Trying to touch userContent rather than some random file, so that we can verify the result remotely.
Reducing rounds to two: one for capability, one for random transport commands.

This is intended to be a true blackbox test: while we customize the client behavior, it can run against any server.

Conflicts:
	cli/src/test/java/hudson/cli/ConnectionTest.java
	pom.xml

Conflicts:
	pom.xml

[FIXED SECURITY-218]

anonymous Callable fails to serialize without this.

jnlpSlave(jenkins.security.Security218Test)  Time elapsed: 3.616 sec  <<< ERROR!
java.io.IOException: Unable to serialize jenkins.security.Security218Test$1@72a2ba17
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1180)
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
    at hudson.remoting.UserRequest._serialize(UserRequest.java:158)
    at hudson.remoting.UserRequest.serialize(UserRequest.java:167)
    at hudson.remoting.UserRequest.<init>(UserRequest.java:63)
    at hudson.remoting.Channel.call(Channel.java:779)
    at jenkins.security.Security218Test.check(Security218Test.java:65)
    at jenkins.security.Security218Test.jnlpSlave(Security218Test.java:55)

Added a test case for master/slave communication.

(cherry picked from commit 88e287a8)