SP-357, BIS-242: Bug fixed. Tests refactored to make them faster.

.../openbis/generic/server/business/RelationshipService.java

...is/generic/server/business/bo/util/RelationshipUtils.java

...cisd/openbis/generic/server/util/TimeIntervalChecker.java

...t/optimistic_locking/ExperimentOptimisticLockingTest.java

...c_locking/MultiThreadExperimentOptimisticLockingTest.java

...imistic_locking/MultiThreadOptimisticLockingTestCase.java

...stic_locking/MultiThreadProjectOptimisticLockingTest.java

...temtest/optimistic_locking/OptimisticLockingTestCase.java

...test/optimistic_locking/ProjectOptimisticLockingTest.java

...x/cisd/openbis/systemtest/optimistic_locking/ToolBox.java