Ignore the environment variable "http_proxy" so that it doesn't interfere with the gRPC-based communication between the Bazel client and server.

--
MOS_MIGRATED_REVID=137138408
diff --git a/src/main/cpp/blaze.cc b/src/main/cpp/blaze.cc
index 7a25bcc..a4519c5 100644
--- a/src/main/cpp/blaze.cc
+++ b/src/main/cpp/blaze.cc
@@ -1361,6 +1361,11 @@
 }
 
 static void CheckEnvironment() {
+  if (getenv("http_proxy") != NULL) {
+    fprintf(stderr, "Warning: ignoring http_proxy in environment.\n");
+    unsetenv("http_proxy");
+  }
+
   if (getenv("LD_ASSUME_KERNEL") != NULL) {
     // Fix for bug: if ulimit -s and LD_ASSUME_KERNEL are both
     // specified, the JVM fails to create threads.  See thread_stack_regtest.