Fix for socket file not being reused even when not bound

In my machine, when I `Ctrl+C` (using falcon supervisor), supervisor.ipc remains and when I restart the server, I get EADDRINUSE

Found that `File.exist?(@path)` is returning false for such a file even though `ls -al` lists the file

Using `FileUtils.safe_unlink` instead of `File.unlink` to safely remove the file when it exists without any error

Author: mintuhouse

lib/async/io/unix_endpoint.rb

@@ -35,8 +35,8 @@ def bind(&block)
 				Socket.bind(@address, **@options, &block)
 			rescue Errno::EADDRINUSE
 				# If you encounter EADDRINUSE from `bind()`, you can check if the socket is actually accepting connections by attempting to `connect()` to it. If the socket is still bound by an active process, the connection will succeed. Otherwise, it should be safe to `unlink()` the path and try again.
-				if !bound? && File.exist?(@path)
-					File.unlink(@path)
+				if !bound?
+					FileUtils.safe_unlink(@path)
 					retry
 				else
 					raise