Upgrade rust/crates/protobuf to 2.17.0

* Android.bp was regenerated. New rustc warnings were found.
* Keep local change in src/lib.rs to include out/version.rs.
* Update out/version.rs to the new version.

Change-Id: I9c2f7d412dcd42fe3769505629e05ab949300fe6
Test: make
diff --git a/METADATA b/METADATA
index ab3c29a..bafbb47 100644
--- a/METADATA
+++ b/METADATA
@@ -9,11 +9,11 @@
     type: GIT
     value: "https://github.com/stepancheg/rust-protobuf"
   }
-  version: "2.16.2"
+  version: "2.17.0"
   license_type: NOTICE
   last_upgrade_date {
     year: 2020
-    month: 7
-    day: 10
+    month: 8
+    day: 12
   }
 }