tools: implement method to send ipmi packet to BMC

Implement method to send ipmi packets to BMC.  Only currently supports
the system interface.

Tested: Verified on a host that has the BLOB handler installed on the
BMC, that it received a blob count of 0, as there were no handlers
installed at that test.  Further functional tests will verify cases with
the firmware handler installed, however, it is verified that this code
correctly speaks IPMI to the BLOB handler registered.

Change-Id: I696f3915930cc9fa5e768fbdeed484ea6cb707a2
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/tools/ipmi_interface.hpp b/tools/ipmi_interface.hpp
index 8be624c..6bad7db 100644
--- a/tools/ipmi_interface.hpp
+++ b/tools/ipmi_interface.hpp
@@ -19,7 +19,7 @@
      * @throws IpmiException on failure.
      */
     virtual std::vector<std::uint8_t>
-        sendPacket(const std::vector<std::uint8_t>& data) = 0;
+        sendPacket(std::vector<std::uint8_t>& data) = 0;
 };
 
 } // namespace host_tool