coverity 1021925: Missing break in switch

Problem:
  CID 1021925 (#1 of 1): Missing break in switch (MISSING_BREAK)
  unterminated_case: The case for value TS_EVENT_VCONN_WRITE_COMPLETE is not terminated by a 'break' statement.

Solution:
  It was intended not to have a break (not a bug), so refactored the code to make coverity happy.

Author: Gancho Tenev

example/cache_scan/cache_scan.cc

@@ -281,21 +281,25 @@ handle_io(TSCont contp, TSEvent event, void * /* edata ATS_UNUSED */)
     }
 
     return 0;
-  }
+  } break;
   case TS_EVENT_VCONN_WRITE_READY: {
     TSDebug(PLUGIN_NAME, "ndone: %" PRId64 " total_bytes: % " PRId64, TSVIONDoneGet(cstate->write_vio), cstate->total_bytes);
     cstate->write_pending = false;
     // the cache scan handler should call vio reenable when there is
     // available data
     // TSVIOReenable(cstate->write_vio);
     return 0;
-  }
-  case TS_EVENT_VCONN_WRITE_COMPLETE:
+  } break;
+  case TS_EVENT_VCONN_WRITE_COMPLETE: {
     TSDebug(PLUGIN_NAME, "write complete");
+    cstate->done = 1;
+    cleanup(contp);
+  } break;
   case TS_EVENT_VCONN_EOS:
-  default:
+  default: {
     cstate->done = 1;
     cleanup(contp);
+  } break;
   }
 
   return 0;