Don't crash if mapper times out

We've seen cases where there is so much going on at once on a system
that the mapper will get too busy and calls to it will time out.

When this happens to virtual-sensors it will core dump and restart, but
eventually over time it can accumulate so many restarts that it will hit
systemd's restart limit and no longer be restarted.

To avoid this, just do the same thing as when the sensor isn't on D-Bus,
which is to ignore that sensor for now and try again the next time the
virtual sensor is calculated.

Change-Id: I6a09fe4c56070f1b23c97f66fe38f3b900e02ee9
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/dbusUtils.hpp b/dbusUtils.hpp
index b664c48..ae95d15 100644
--- a/dbusUtils.hpp
+++ b/dbusUtils.hpp
@@ -42,6 +42,11 @@
             // The service isn't on D-Bus yet.
             return std::string{};
         }
+        else if (ex.name() == std::string("org.freedesktop.DBus.Error.Timeout"))
+        {
+            lg2::info("Mapper timeout while looking up {PATH}", "PATH", path);
+            return std::string{};
+        }
 
         throw;
     }