Use forked version of grpcio (pantsbuild#6344)

This includes tikv/grpc-rs#211 which stops us
seeing RpcFinished errors when the server responds very quickly to
requests.

Unfortunately, this will slow down building pants, as you'll need to
checkout the git repository, but that should be a once-per-machine cost.

src/rust/engine/fs/Cargo.toml

@@ -13,7 +13,8 @@ digest = "0.6.2"
 futures = "^0.1.16"
 futures-cpupool = "0.1"
 glob = "0.2.11"
-grpcio = { version = "0.3", features = ["secure"] }
+# Pull in https://github.com/pingcap/grpc-rs/pull/211
+grpcio = { git = "https://github.com/illicitonion/grpc-rs.git", rev = "d106c615bc0c289ba6d1ce6871786266d109c31c", features = ["secure"] }
 hashing = { path = "../hashing" }
 ignore = "0.3.1"
 indexmap = "1"

src/rust/engine/process_execution/Cargo.toml

@@ -12,7 +12,8 @@ bytes = "0.4.5"
 digest = "0.6.2"
 fs = { path = "../fs" }
 futures = "^0.1.16"
-grpcio = { version = "0.3", features = ["secure"] }
+# Pull in https://github.com/pingcap/grpc-rs/pull/211
+grpcio = { git = "https://github.com/illicitonion/grpc-rs.git", rev = "d106c615bc0c289ba6d1ce6871786266d109c31c", features = ["secure"] }
 hashing = { path = "../hashing" }
 log = "0.4"
 protobuf = { version = "2.0.4", features = ["with-bytes"] }

src/rust/engine/process_execution/bazel_protos/Cargo.toml

@@ -7,7 +7,8 @@ publish = false
 [dependencies]
 bytes = "0.4.5"
 futures = "^0.1.16"
-grpcio = { version = "0.3", features = ["secure"] }
+# Pull in https://github.com/pingcap/grpc-rs/pull/211
+grpcio = { git = "https://github.com/illicitonion/grpc-rs.git", rev = "d106c615bc0c289ba6d1ce6871786266d109c31c", features = ["secure"] }
 hashing = { path = "../../hashing" }
 protobuf = { version = "2.0.4", features = ["with-bytes"] }
 

src/rust/engine/testutil/mock/Cargo.toml

@@ -8,7 +8,8 @@ publish = false
 bazel_protos = { path = "../../process_execution/bazel_protos" }
 bytes = "0.4.5"
 futures = "^0.1.16"
-grpcio = { version = "0.3", features = ["secure"] }
+# Pull in https://github.com/pingcap/grpc-rs/pull/211
+grpcio = { git = "https://github.com/illicitonion/grpc-rs.git", rev = "d106c615bc0c289ba6d1ce6871786266d109c31c", features = ["secure"] }
 hashing = { path = "../../hashing" }
 protobuf = { version = "2.0.4", features = ["with-bytes"] }
 testutil = { path = ".." }