Improve external lock implementation

Remove a number of limitations from the external locks.
- They can be nested now
- They do not need external cleanup in case of failures
- They do not rely on lockfile or greenlet internal implementation

New implementation is based on fcntl locks and any crashing process
will drop the lock. It does not have to rely on any cleanup code or
handling exceptions. Because no cleanup is needed, a number of tests
have been removed.
This implementation is not portable outside of POSIX/BSD/SVR4 systems.

Fcntl locks should work correctly with NFS mounts.

Locks are cleaned up after the tests finish running via run_tests.sh,
even though it's not strictly needed.

This change requires eventlet >= 0.9.17.

bp improve-external-locking

Change-Id: Idf5424c04645f25097733848a007b150145b0b27

0 files changed, 0 insertions, 0 deletions