vhost: impl From<UnixListener> for Listener

It was already possible to do this as follows:

	unsafe { Listener::from_raw_fd(listener.into_raw_fd()) }

This just factors the From implementation out of the FromRawFd
implementation so it's possible to do the conversion without an
unnecessary unsafe in application code.

Signed-off-by: Alyssa Ross <hi@alyssa.is>

Author: alyssais

vhost/CHANGELOG.md

@@ -3,6 +3,9 @@
 ## [Unreleased]
 
 ### Added
+- [[#311]](https://github.com/rust-vmm/vhost/pull/311) Implement
+  `From<UnixListener>` for `vhost_user::Listener`.
+
 ### Changed
 ### Deprecated
 ### Fixed

vhost/src/vhost_user/connection.rs

@@ -86,10 +86,13 @@ impl AsRawFd for Listener {
 
 impl FromRawFd for Listener {
     unsafe fn from_raw_fd(fd: RawFd) -> Self {
-        Listener {
-            fd: UnixListener::from_raw_fd(fd),
-            path: None,
-        }
+        Self::from(UnixListener::from_raw_fd(fd))
+    }
+}
+
+impl From<UnixListener> for Listener {
+    fn from(fd: UnixListener) -> Self {
+        Self { fd, path: None }
     }
 }