Depend on official gnmi repo instead of fork

No need to maintain a separate fork of gnmi when what we need can be
achieved with a simple Bazel rule

Change-Id: I94ce6f617306e8fb68c44ec2a64743996d3c2f38
diff --git a/tools/build/bazel/gnmi_BUILD b/tools/build/bazel/gnmi_BUILD
index 43cb693..8ce0ac8 100644
--- a/tools/build/bazel/gnmi_BUILD
+++ b/tools/build/bazel/gnmi_BUILD
@@ -1,6 +1,9 @@
+# Prefix string to remove from proto import statements
+IMPORT_PREFIX = "github.com/openconfig/gnmi/proto/"
+
 proto_library(
     name = "gnmi_proto",
-    srcs = ["gnmi/gnmi.proto"],
+    srcs = [":gnmi_proto_sed"],
     deps = [
         ":gnmi_ext_proto",
         "@com_google_protobuf//:descriptor_proto",
@@ -9,9 +12,17 @@
     visibility = ["//visibility:public"],
 )
 
-
 proto_library(
     name = "gnmi_ext_proto",
     srcs = ["gnmi_ext/gnmi_ext.proto"],
     visibility = ["//visibility:public"],
 )
+
+
+genrule(
+    name = "gnmi_proto_sed",
+    srcs = [":gnmi/gnmi.proto"],
+    outs = ["new/gnmi/gnmi.proto"],
+    cmd = "sed -e 's:import \"%s:import \":g' $(location :gnmi/gnmi.proto) > \"$@\""
+        % IMPORT_PREFIX,
+)