Use time mode owner enums in dbus interface

Dbus interface defines time mode owners in xyz::openbmc_project::Time.
Use the enums from the interface instead of repo defined enums and use
the generated code to do convertions between strings and enums.

Update unit tests accordingly.

Change-Id: Ic304aa3b4137375d208bb1702e0f64df512fc5a0
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/utils.hpp b/utils.hpp
index 87bc2bf..5d72155 100644
--- a/utils.hpp
+++ b/utils.hpp
@@ -108,7 +108,9 @@
 /** @brief Convert a string to enum Mode
  *
  * Convert the time mode string to enum.
- * Valid strings are "NTP", "MANUAL"
+ * Valid strings are
+ *   "xyz.openbmc_project.Time.Synchronization.Method.NTP"
+ *   "xyz.openbmc_project.Time.Synchronization.Method.Manual"
  * If it's not a valid time mode string, it means something
  * goes wrong so raise exception.
  *
@@ -121,7 +123,11 @@
 /** @brief Convert a string to enum Owner
  *
  * Convert the time owner string to enum.
- * Valid strings are "BMC", "HOST", "SPLIT", "BOTH"
+ * Valid strings are
+ *   "xyz.openbmc_project.Time.Owner.Owners.BMC"
+ *   "xyz.openbmc_project.Time.Owner.Owners.Host"
+ *   "xyz.openbmc_project.Time.Owner.Owners.Both"
+ *   "xyz.openbmc_project.Time.Owner.Owners.Split"
  * If it's not a valid time owner string, it means something
  * goes wrong so raise exception.
  *
@@ -137,7 +143,7 @@
  *
  * @return The string of the mode
  */
-const char* modeToStr(Mode mode);
+std::string modeToStr(Mode mode);
 
 /** @brief Convert a owner enum to owner string
  *
@@ -145,7 +151,7 @@
  *
  * @return The string of the owner
  */
-const char* ownerToStr(Owner owner);
+std::string ownerToStr(Owner owner);
 
 } // namespace utils
 } // namespace time