healthd: fix runstring option error reporting

Change-Id: I548d837afbde8a66826bb2cdb79ede7edda42b1f
diff --git a/healthd/healthd.cpp b/healthd/healthd.cpp
index 095ce9d..8363c41 100644
--- a/healthd/healthd.cpp
+++ b/healthd/healthd.cpp
@@ -342,7 +342,8 @@
                 break;
             case '?':
             default:
-                KLOG_ERROR(LOG_TAG, "Unrecognized healthd option: %c\n", ch);
+                KLOG_ERROR(LOG_TAG, "Unrecognized healthd option: %c\n",
+                           optopt);
                 exit(1);
             }
         }