Need to add patient verification to return Cohorts objects for the serviceMethods

In reporting compatibility module used the org.openmrs.cohort.Cohort class instead of org.openmrs.Cohort class. So other modules which are using these service methods needed to add the reporting compatibility module as the required module. 

To avoid this requirement, A patient verification is added to the Cohort Membership methods.

Dev Notes

Just check for the MembershipIds in the Cohort class, and remove it from the Cohort membersberIds if it is null.