Admission controller: logging improvements

Some of the less verbose debug information is now log level 2. Also improved
the debug message logged when a request comes in to make it easier to read.

Change-Id: I0ab96d12f94ee52910995d85328aa401a9c77a65
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1897
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins