Build broken against 2.6.0-SNAPSHOT due to new abstract methods added by YARN-2229

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:testCompile (default-testCompile) on project slider-core: Compilation failure: Compilation failure:
[ERROR] /homes/hortonzy/slider/slider-core/src/test/groovy/org/apache/slider/server/appmaster/model/mock/MockContainerId.groovy:[24,7] 1. ERROR in /homes/hortonzy/slider/slider-core/src/test/groovy/org/apache/slider/server/appmaster/model/mock/MockContainerId.groovy (at line 24)
[ERROR] class MockContainerId extends ContainerId implements Cloneable {
[ERROR] ^^^^^^^^^^^^^^^
[ERROR] Groovy:Can't have an abstract method in a non-abstract class. The class 'org.apache.slider.server.appmaster.model.mock.MockContainerId' must be declared abstract or the method 'void setContainerId(long)' must be implemented.
[ERROR]
[ERROR] /homes/hortonzy/slider/slider-core/src/test/groovy/org/apache/slider/server/appmaster/model/mock/MockContainerId.groovy:[24,7] 2. ERROR in /homes/hortonzy/slider/slider-core/src/test/groovy/org/apache/slider/server/appmaster/model/mock/MockContainerId.groovy (at line 24)
[ERROR] class MockContainerId extends ContainerId implements Cloneable {
[ERROR] ^^^^^^^^^^^^^^^
[ERROR] Groovy:Can't have an abstract method in a non-abstract class. The class 'org.apache.slider.server.appmaster.model.mock.MockContainerId' must be declared abstract or the method 'long getContainerId()' must be implemented.
[ERROR]
[ERROR] Found 2 errors and 0 warnings.