Clarify usage of lraUid versus lraId in the code

As part of the JBTM-3378 there was created a unified method for for getting LRA uid from the LRA id. This method was put under LRAConstants as method getLRAid . This is a wrong name as the method extracts the uid part of the LRA id. It needs to be renamed for not making misunderstanding of the code. On top of it it may throw NPE when the provided LRA id - which is represented by URI - does not contain path component. There should not be NPE but rather some descriptive RuntimeException being used.