RFR: JDK-8068225: nsk/jdi/EventQueue/remove_l/remove_l005 intermittently times out

[Gary Adams]

The intermittent failures for remove_l005 appears to be due to a timing 
issue
in the shutdown handling after the test has completed. The debugger has sent
a "quit" command, but the debugee has not completed processing the command
and exited as expected.

This proposed change modifies the Debugee.endDebugee() processing to
wait for the debuggee to complete before doing the tear down processing
on the debugger side of the connection. This sequencing did expose
an issue in the canBeModified test, where the debugee was never resumed
after the VMStart event was detected. Resuming the debugee allows it to
respond as expected when the direct call to endDebugee is invoked.

Testing is still in progress, but it looks like this will resolve a 
number of
tail end intermittent failures.

   Issue: https://bugs.openjdk.java.net/browse/JDK-8068225
   Webrev: http://cr.openjdk.java.net/~gadams/8068225/webrev.00/