Two task_finder cleanups.

Two task_finder cleanups.

* runtime/task_finder.c: Two cleanup fixes. Merged 2 different state
  variables into 1. Reversed utrace compatibility fix.  Instead of
  making new utrace look like old utrace, made old utrace look like new
  utrace (i.e. use 'utrace_engine' instead of 'utrace_attached_engine').
* runtime/utrace_compatibility.h: Reversed utrace compatibility fix (use
  'utrace_engine' instead of 'utrace_attached_engine').