add a flag to run tradefed in debug mode, generate debug info

This add a flag tradefed script, so that when starting tradefed,
the JVM will wait for a debugger to attach first.

Change-Id: Ib2509561e435015a8edb9fb2972097873f366d8f
Example:
  * run:
    TF_DEBUG=1 tools/tradefederation/tradefed.sh
  * Create a remote debugging profile to use tradefed source and connect
    to port 10088
3 files changed