cold_redundancy: Fix build failures

The cold_redundancy application began failing to build recently due to
missing boost::asio includes.

I believe the cause is a change to some sdbusplus header files.  The
sdbusplus header files previously included the convenience header file
"boost/asio.hpp".  However, the sdbusplus header files now include more
specific boost header files.  See
https://github.com/openbmc/sdbusplus/commit/38ab5ecfe3c51501a9380e2c30dbb5fdd88cf4f9
for more information.

The cold_redundancy source files appeared to have been relying on
sdbusplus to include the convenience header.  They do not include header
files for some of the boost asio classes they are using.

I did not write any of the cold_redundancy application and do not have
the ability to test it.  For this reason, I made the simple change of
adding an include of "boost/asio.hpp" to the cold_redundancy header file
that needed it.  This would seem to be a safe change, since it
effectively 'undoes' the change made in sdbusplus.  The maintainers of
this application may wish to push up another commit that replaces this
with more specific includes.

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: I42154d621fcf125f95a639375d3749dbd7dcd91d
diff --git a/cold-redundancy/cold_redundancy.hpp b/cold-redundancy/cold_redundancy.hpp
index cfceff2..b72c642 100644
--- a/cold-redundancy/cold_redundancy.hpp
+++ b/cold-redundancy/cold_redundancy.hpp
@@ -14,6 +14,7 @@
 // limitations under the License.
 */
 
+#include <boost/asio.hpp>
 #include <sdbusplus/asio/object_server.hpp>
 #include <util.hpp>