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/gnmi/ctl/BUILD b/protocols/gnmi/ctl/BUILD
index 482a37f..a82dafd 100644
--- a/protocols/gnmi/ctl/BUILD
+++ b/protocols/gnmi/ctl/BUILD
@@ -3,7 +3,7 @@
     "//protocols/gnmi/stub:onos-protocols-gnmi-stub",
     "//protocols/grpc/api:onos-protocols-grpc-api",
     "//protocols/grpc/ctl:onos-protocols-grpc-ctl",
-    "//lib:io_grpc_grpc_core_context",
+    "//lib:io_grpc_grpc_api_context",
     "//lib:com_google_protobuf_protobuf_java",
     "//lib:io_grpc_grpc_netty",
     "//lib:io_grpc_grpc_protobuf_lite",
@@ -13,7 +13,7 @@
 
 TEST_DEPS = TEST + [
     "@minimal_json//jar",
-    "//lib:io_grpc_grpc_core_context",
+    "//lib:io_grpc_grpc_api_context",
     "//lib:io_grpc_grpc_protobuf_lite",
 ]