Env.vars: server won't ignore the client env

Make the --ignore_client_env flag a no-op.
The client will pass --client_env flags to the
server even in --batch mode. This simplifies the
code as well as ensuring that the server always
uses the up-do-date client environment.

We'll gradually get rid of all System.getenv calls
in the server, because the server should always
respect the client env.

Roll forward of 149403129 with fixes.

--
PiperOrigin-RevId: 149435060
MOS_MIGRATED_REVID=149435060
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/CommonCommandOptions.java b/src/main/java/com/google/devtools/build/lib/runtime/CommonCommandOptions.java
index fb521ae..2afb774 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/CommonCommandOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/CommonCommandOptions.java
@@ -20,7 +20,6 @@
 import com.google.devtools.common.options.Option;
 import com.google.devtools.common.options.OptionsBase;
 import com.google.devtools.common.options.OptionsParsingException;
-
 import java.util.List;
 import java.util.Map;
 import java.util.logging.Level;
@@ -128,7 +127,11 @@
   @Option(name = "ignore_client_env",
       defaultValue = "false",
       category = "hidden",
-      help = "If true, ignore the '--client_env' flag, and use the JVM environment instead")
+      deprecationWarning = "Deprecated, no-op.",
+      help = "Deprecated, no-op."
+  )
+  // TODO(laszlocsomor, dslomov) 2017-03-07: remove this flag after 2017-06-01 (~3 months from now)
+  // and all of its occurrences.
   public boolean ignoreClientEnv;
 
   @Option(name = "client_cwd",