EJBCLIENT-104: run tests with security manager and provide fixes

https://issues.jboss.org/browse/EJBCLIENT-104
Stuart already fixed the main issue. The PR contains a full set of fixes and tests.
Else you would get this error: 
`access: domain that failed ProtectionDomain  (file:/home/carlo/work/jboss/jboss-ejb-client/target/test-classes/ <no signer certificates>)`
...
```
java.lang.ExceptionInInitializerError
	at org.jboss.ejb.client.remoting.ConfigBasedEJBClientContextSelector.<init>(ConfigBasedEJBClientContextSelector.java:88)
	at org.jboss.ejb.client.remoting.ConfigBasedEJBClientContextSelector.<init>(ConfigBasedEJBClientContextSelector.java:71)
	at org.jboss.ejb.client.test.reconnect.ReconnectTestCase.testReconnectOfBrokenConnection(ReconnectTestCase.java:158)
...
Caused by: java.lang.RuntimeException: java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "accessDeclaredMembers")
	at java.util.concurrent.atomic.AtomicReferenceFieldUpdater$AtomicReferenceFieldUpdaterImpl.<init>(AtomicReferenceFieldUpdater.java:219)
	at java.util.concurrent.atomic.AtomicReferenceFieldUpdater.newUpdater(AtomicReferenceFieldUpdater.java:95)
	at org.jboss.ejb.client.EJBClientContext.<clinit>(EJBClientContext.java:80)
	... 29 more
Caused by: java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "accessDeclaredMembers")
	at java.security.AccessControlContext.checkPermission(AccessControlContext.java:372)
	at java.security.AccessController.checkPermission(AccessController.java:559)
	at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
	at java.lang.Class.checkMemberAccess(Class.java:2276)
	at java.lang.Class.getDeclaredField(Class.java:1945)
	at java.util.concurrent.atomic.AtomicReferenceFieldUpdater$AtomicReferenceFieldUpdaterImpl.<init>(AtomicReferenceFieldUpdater.java:212)
	... 31 more


java.lang.NoClassDefFoundError: Could not initialize class org.jboss.ejb.client.EJBClientContext
	at org.jboss.ejb.client.remoting.ConfigBasedEJBClientContextSelector.<init>(ConfigBasedEJBClientContextSelector.java:88)
	at org.jboss.ejb.client.remoting.ConfigBasedEJBClientContextSelector.<init>(ConfigBasedEJBClientContextSelector.java:71)
	at org.jboss.ejb.client.test.reconnect.ReconnectTestCase.testReconnectOfNotYetStartedServer(ReconnectTestCase.java:87)
...
```
In the current test set this doesn't occur because I had to add the permission for another issue in Xnio.