HHH-18755 - Skip test that causes deadlock

On CockroachDB the method
`testCopyPersistentCollectionReferenceAfterFlush` causes a
deadlock, which is resolved eventually by a TimeoutException.

This problem has been discussed in
cockroachdb/cockroach#61269. The
CockroachDB developers do not see this as a bug that needs to
be fixed. Therefore we skip this test for CockroachDB.

hibernate-core/src/test/java/org/hibernate/orm/test/collection/multisession/MultipleSessionCollectionTest.java

@@ -19,6 +19,7 @@
 import org.hibernate.Hibernate;
 import org.hibernate.collection.spi.AbstractPersistentCollection;
 import org.hibernate.collection.spi.PersistentCollection;
+import org.hibernate.dialect.CockroachDialect;
 import org.hibernate.dialect.HSQLDialect;
 import org.hibernate.engine.spi.CollectionEntry;
 
@@ -95,6 +96,7 @@ public void testCopyPersistentCollectionReferenceBeforeFlush(SessionFactoryScope
 	@Test
 	@JiraKey("HHH-9518")
 	@SkipForDialect(dialectClass = HSQLDialect.class, reason = "The select triggered by the merge just hang without any exception")
+	@SkipForDialect(dialectClass = CockroachDialect.class, reason = "The merge in the second session causes a deadlock")
 	public void testCopyPersistentCollectionReferenceAfterFlush(SessionFactoryScope scope) {
 		Parent p = new Parent();
 		Child c = new Child();