tools: put all host-side code into host_tool namespace

To avoid confusion and organize the code itself more cleanly, place the
host-side code into its own namespace.

Change-Id: I573eb0494eb59874adb1d1eadc502499e928e396
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/test/ipmi_interface_mock.hpp b/test/ipmi_interface_mock.hpp
index 2fac71d..409ef44 100644
--- a/test/ipmi_interface_mock.hpp
+++ b/test/ipmi_interface_mock.hpp
@@ -4,6 +4,9 @@
 
 #include <gmock/gmock.h>
 
+namespace host_tool
+{
+
 class IpmiInterfaceMock : public IpmiInterface
 {
   public:
@@ -11,3 +14,5 @@
     MOCK_METHOD1(sendPacket,
                  std::vector<std::uint8_t>(const std::vector<std::uint8_t>&));
 };
+
+} // namespace host_tool