shill: Fix most of warnings from cpplint

Fix most cpplinter's warnings. On a few occasisions, the warnings
produced were false-positives, so added explicit // NOLINT comment
overrides.

There were a few instances of disallowed non-const reference usage
(reported as runtime/reference error by cpplint) for
"DBus::Error &error" which should potentially be changed
to pointers to comply with C++ coding style but I will let Shill
owners do that since there is quite a few of those and the
change isn't brain-dead simple...

BUG=None
TEST=platform2 still compiles and all unit tests pass.

Change-Id: Ic2e31896aa13d20eeb1a85dee74f3db8cccfde2e
Reviewed-on: https://chromium-review.googlesource.com/204164
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/dhcp_config_unittest.cc b/dhcp_config_unittest.cc
index 8da3339..5dbaa70 100644
--- a/dhcp_config_unittest.cc
+++ b/dhcp_config_unittest.cc
@@ -4,6 +4,9 @@
 
 #include "shill/dhcp_config.h"
 
+#include <string>
+#include <vector>
+
 #include <base/bind.h>
 #include <base/file_util.h>
 #include <base/files/scoped_temp_dir.h>
@@ -47,7 +50,7 @@
 const bool kHasHostname = true;
 const bool kHasLeaseSuffix = true;
 const bool kMinimalConfig = true;
-}  // namespace {}
+}  // namespace
 
 class DHCPConfigTest : public PropertyStoreTest {
  public:
@@ -435,7 +438,7 @@
 
 void DoNothing() {}
 
-}  // namespace {}
+}  // namespace
 
 TEST_F(DHCPConfigCallbackTest, ProcessEventSignalFail) {
   DHCPConfig::Configuration conf;