Added EINTR handling for FcntlFlock call.
Added EINTR handling for FcntlFlock call.

This commit adds EINTR handling for file locking. This may become more
necessary with Go 1.14's new preemption.

Signed-off-by: Jacob Howard <f862f167b85d41b225785c70d70808bc7337c1fe@havoc.io>

havoc-io/mutagen,havoc-io/mutagen