Use language agnostic heuristic to check if monero_wallet_rpc is ready

Our strategy of searching for a english string to determine if
monero_wallet_rpc is ready is not compatible with languages other than
english. Instead we assume the monero rpc is ready if it has stopped
writing to stdout. We make a json rpc request to confirm this. A better
solution would have been to configure the monero_wallet_rpc to always
output in english but there is not command line argument to configure
the language.

Closes #353.

monero-rpc/src/rpc/wallet.rs

@@ -357,6 +357,24 @@ impl Client {
         let r = serde_json::from_str::<Response<SweepAll>>(&response)?;
         Ok(r.result)
     }
+
+    pub async fn get_version(&self) -> Result<Version> {
+        let request = Request::new("get_version", "");
+
+        let response = self
+            .inner
+            .post(self.url.clone())
+            .json(&request)
+            .send()
+            .await?
+            .text()
+            .await?;
+
+        debug!("get_version RPC response: {}", response);
+
+        let r = serde_json::from_str::<Response<Version>>(&response)?;
+        Ok(r.result)
+    }
 }
 
 #[derive(Serialize, Debug, Clone)]
@@ -512,6 +530,11 @@ pub struct SweepAll {
     weight_list: Vec<u32>,
 }
 
+#[derive(Debug, Copy, Clone, Deserialize)]
+pub struct Version {
+    version: u32,
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;