Upgrade Mockito to 2.25.0 for Java 11 compatibility

[wborn]

Currently the first exceptions that occur in a Java 11 build are due to Mockito/Byte Buddy being incompatible with Java 11:

Mockito cannot mock this class: interface java.lang.Runnable.

Mockito can only mock non-private & non-final classes.
If you're not sure why you're getting this error, please report to the mailing list.


Java               : 11
JVM vendor name    : Oracle Corporation
JVM vendor version : 11.0.1+13
JVM name           : OpenJDK 64-Bit Server VM
JVM version        : 11.0.1+13
JVM info           : mixed mode
OS name            : Linux
OS version         : 4.15.0-1026-gcp


Underlying exception : java.lang.UnsupportedOperationException: Cannot define class using reflection
	at org.eclipse.smarthome.test.java.JavaTestTest.waitForAssertShouldRunAfterLastCall_whenAssertionSucceeds(JavaTestTest.java:38)
Caused by: java.lang.UnsupportedOperationException: Cannot define class using reflection
	at org.eclipse.smarthome.test.java.JavaTestTest.waitForAssertShouldRunAfterLastCall_whenAssertionSucceeds(JavaTestTest.java:38)
Caused by: java.lang.IllegalStateException: Could not find sun.misc.Unsafe
	at org.eclipse.smarthome.test.java.JavaTestTest.waitForAssertShouldRunAfterLastCall_whenAssertionSucceeds(JavaTestTest.java:38)
Caused by: java.lang.NoSuchMethodException: sun.misc.Unsafe.defineClass(java.lang.String, [B, int, int, java.lang.ClassLoader, java.security.ProtectionDomain)
	at org.eclipse.smarthome.test.java.JavaTestTest.waitForAssertShouldRunAfterLastCall_whenAssertionSucceeds(JavaTestTest.java:38)

After upgrading Mockito these exceptions are resolved. The stacktraces then show that next Xtext needs to be upgraded to 2.17 (#646) to make the Java 11 build more successful.

We'll also need to update the itests dependencies in openhab2-addons.

[maggu2810]

@wborn Will you update the addons integration tests as soon as I press the button?

[wborn]

I already did it before you pushed the button. 😉

See: https://github.com/openhab/openhab2-addons/pull/5102