fix include names

cppcheck isn't smart enough to recognize these are c++ headers, not c
headers.  Considering we're already inconsistent about our naming, it's
easier to just be consistent, and move the last few files to use .hpp
instead of .h.

Tested:
Code builds, no changes.

Signed-off-by: Ed Tanous <ed@tanous.net>
Change-Id: Ic348d695f8527fa4a0ded53f433e1558c319db40
diff --git a/include/nbd_proxy.hpp b/include/nbd_proxy.hpp
index e2ebba1..7ad80a6 100644
--- a/include/nbd_proxy.hpp
+++ b/include/nbd_proxy.hpp
@@ -14,9 +14,7 @@
 // limitations under the License.
 */
 #pragma once
-#include <app.h>
-#include <websocket.h>
-
+#include <app.hpp>
 #include <boost/asio/buffer.hpp>
 #include <boost/asio/local/stream_protocol.hpp>
 #include <boost/asio/write.hpp>
@@ -25,6 +23,7 @@
 #include <boost/container/flat_map.hpp>
 #include <dbus_utility.hpp>
 #include <privileges.hpp>
+#include <websocket.hpp>
 
 #include <variant>