util::dbus: Make common the transition host support

Move transition host support from attention handler specific code to
common util code.

Signed-off-by: Ben Tyner <ben.tyner@ibm.com>
Change-Id: I7fb4970354aaeca65fcc074107f99262e504ac34
diff --git a/util/dbus.hpp b/util/dbus.hpp
index 03fb5be..66a2ad4 100644
--- a/util/dbus.hpp
+++ b/util/dbus.hpp
@@ -64,6 +64,23 @@
  */
 std::vector<std::string> systemNames();
 
+/** @brief Host states for util::dbus host state operations */
+enum class HostState
+{
+    Quiesce,
+    Diagnostic,
+    Crash
+};
+
+/**
+ * @brief Transition the host state
+ *
+ * We will transition the host state by starting the appropriate dbus target.
+ *
+ * @param i_hostState the state to transition the host to
+ */
+void transitionHost(const HostState i_hostState);
+
 } // namespace dbus
 
 } // namespace util