Update Tokio to Rust 2018 (#1082)

ci/azure-tsan.yml

@@ -12,7 +12,7 @@ jobs:
   steps:
   - template: azure-install-rust.yml
     parameters:
-      rust_version: nightly-2018-11-18
+      rust_version: ${{ parameters.rust }}
 
   - template: azure-patch-crates.yml
   - script: |

ci/tsan

@@ -8,6 +8,8 @@ race:Weak*drop
 # `std` mpsc is not used in any Tokio code base. This race is triggered by some
 # rust runtime logic.
 race:std*mpsc_queue
+race:std*lang_start
+race:drop*std::thread*
 
 # Probably more fences in std.
 race:__call_tls_dtors