Follow on to r1642698.
Only currently running contexts should be returned.
Handle the case where the mapper returns an unwanted  non-exact match.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc8.0.x/trunk@1644992 13f79535-47bb-0310-9956-ffa450edef68
Whoops. Null check.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc8.0.x/trunk@1645014 13f79535-47bb-0310-9956-ffa450edef68