The problem was a race condition in a test case.

The fix eliminates the race condition by explicit
wait on UNIX socket to start accepting connections.

The patch affects only test suite (i.e. does not touch
server codebase).


mysql-test/mysql-test-run.pl:
  Expose necessary environment variables.
mysql-test/r/im_daemon_life_cycle.result:
  Update result file.
mysql-test/t/im_daemon_life_cycle.imtest:
  Wait for Instance Manager to start accepting connections
  after restart.
mysql-test/t/wait_for_socket.sh:
  Helper script: waits for UNIX socket to start accepting connections.