Bump tokio from 0.2.15 to 0.2.16

Bumps [tokio](https://github.com/tokio-rs/tokio) from 0.2.15 to 0.2.16.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](https://github.com/tokio-rs/tokio/compare/tokio-0.2.15...tokio-0.2.16)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Cargo.lock

@@ -1681,9 +1681,9 @@ dependencies = [
 
 [[package]]
 name = "tokio"
-version = "0.2.15"
+version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "619cdb2245c40c42d563089b72e80c5df659513d667a017598439ef7a7b1ffe1"
+checksum = "ee5a0dd887e37d37390c13ff8ac830f992307fe30a1fff0ab8427af67211ba28"
 dependencies = [
  "bytes",
  "fnv",