Principals are not added if they are already bound.
Principals are not added if they are already bound.

git-svn-id: ec6ef1d57ec0831ce4cbff3b75527511e63bfbe3@710474 13f79535-47bb-0310-9956-ffa450edef68

haxwell/apache-shiro-1.2.3,yaotj/shiro,relateiq/shiro,Collaborne/shiro,universsky/shiro,taoguan/shiro,ivansun1010/shiro,lucamilanesio/shiro,IBYoung/shiro,Kevin2030/shiro,borigue/shiro,chapmajs/shiro,StempG/shiro,apache/jsecurity