[CXF-5251] - Implement more stringent requirements on allowing OnBehalfOf/ActAs in the STS

Conflicts:
	services/sts/sts-core/src/main/java/org/apache/cxf/sts/operation/TokenIssueOperation.java
	services/sts/sts-core/src/test/java/org/apache/cxf/sts/operation/IssueOnbehalfofUnitTest.java
	services/sts/systests/basic/src/test/java/org/apache/cxf/systest/sts/issueunit/IssueUnitTest.java
	services/sts/systests/basic/src/test/resources/org/apache/cxf/systest/sts/deployment/cxf-transport.xml


Conflicts:
	services/sts/sts-core/src/main/java/org/apache/cxf/sts/operation/AbstractOperation.java
	services/sts/sts-core/src/main/java/org/apache/cxf/sts/operation/TokenIssueOperation.java
	services/sts/systests/basic/src/test/java/org/apache/cxf/systest/sts/issueunit/IssueUnitTest.java
	services/sts/systests/basic/src/test/resources/org/apache/cxf/systest/sts/deployment/cxf-transport.xml

git-svn-id: https://svn.apache.org/repos/asf/cxf/branches/2.6.x-fixes@1520300 13f79535-47bb-0310-9956-ffa450edef68