TS-1587 make check fails on the esi plugin

Basically 3 problems

* output_data_len is not initialized in processor_test.cc
* usePackNodeList() function returns a enumeration, not a
 boolean
* The Stub handler manager file is using the same file
 name as the original file, thus causing a conflict. I
 need to rename that file to a different name -
 TestHandlerManager.cc and make sure the test program are
 compiled/linked with that one.