First attempt at supporting builds with Java 11

Includes:
- Bump protobuf to 3.8.0 and grpc-java to 1.21.0 (along with transitive
  dependencies such as Netty)
- Add jaxb_api at compile time when needed (removed in JDK 11)
- Bump Bnd to 4.1 (adds support for Java 11)

To build with JDK 11, uncomment lines in .bazelrc.
Tested with Bazel 0.26.0.

Change-Id: Ib8e0c7310eacf97328762606e57c01e4834e5565
diff --git a/protocols/p4runtime/api/BUILD b/protocols/p4runtime/api/BUILD
index 47a4dd2..b958045 100644
--- a/protocols/p4runtime/api/BUILD
+++ b/protocols/p4runtime/api/BUILD
@@ -1,6 +1,6 @@
 COMPILE_DEPS = CORE_DEPS + [
     "//protocols/grpc/api:onos-protocols-grpc-api",
-    "//lib:io_grpc_grpc_core_context",
+    "//lib:io_grpc_grpc_api_context",
 ]
 
 TEST_DEPS = TEST + [