Use correctly the go scheduler when reading the netlink file descriptor

[pilebones]

Use correctly the go scheduler when reading the netlink file descriptor.

By this way, the scheduler go could manage the select block (from monitor mode) correctly because when reading using the os.File abstraction layer the system interruptions is done by the go runtime.

For this we should:

• With: https://github.com/pilebones/go-udev/blob/master/netlink/conn.go#L40
• Set non-blocking mode for this fd with: https://golang.org/pkg/syscall/#SetNonblock
• Wrap it using : https://golang.org/pkg/os/#NewFile
• Now: https://golang.org/pkg/os/#File.SetDeadline (works)
• Change msg Peek using os.File.Read: https://github.com/pilebones/go-udev/blob/master/netlink/conn.go#L169