Fix bug in force-unwrapping when resetting timers

When running tests locally, this error can surface.

```
---- test::agent_test::custom_resolver stdout ----
thread 'test::agent_test::custom_resolver' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 22, kind: InvalidInput, message: "Invalid argument" }', src/stream.rs:60:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

The problem is that setting the timeouts might fail, and this is done
in a From trait where there is not possibility to "bubble" the
io::Error.

```
socket.set_read_timeout(None).unwrap();
socket.set_write_timeout(None).unwrap();
```

This commit moves the resetting of timers to an explicit `Stream::reset()` fn
that must be called every time we're unwrapping the inner stream.

src/stream.rs

@@ -53,14 +53,7 @@ impl DeadlineStream {
 
 impl From<DeadlineStream> for Stream {
     fn from(deadline_stream: DeadlineStream) -> Stream {
-        // Since we are turning this back into a regular, non-deadline Stream,
-        // remove any timeouts we set.
-        let stream = deadline_stream.stream;
-        if let Some(socket) = stream.socket() {
-            socket.set_read_timeout(None).unwrap();
-            socket.set_write_timeout(None).unwrap();
-        }
-        stream
+        deadline_stream.stream
     }
 }
 
@@ -159,6 +152,17 @@ impl Stream {
         }
     }
 
+    pub(crate) fn reset(&mut self) -> io::Result<()> {
+        // When we are turning this back into a regular, non-deadline Stream,
+        // remove any timeouts we set.
+        if let Some(socket) = self.socket() {
+            socket.set_read_timeout(None)?;
+            socket.set_write_timeout(None)?;
+        }
+
+        Ok(())
+    }
+
     pub(crate) fn socket(&self) -> Option<&TcpStream> {
         match self {
             Stream::Http(b) => Some(b.get_ref()),