fix STR bugs and improve code

- Reset reply size after returning a reply
- Reset data link layer and flush RX for regular commands and before
  performing special commands to ensure consistent start state
- Clean up DHB a bit
- Set STR dev to OFF in assembly when it is faulty.

mission/system/acs/StrAssembly.cpp

@@ -11,8 +11,13 @@ StrAssembly::StrAssembly(object_id_t objectId) : AssemblyBase(objectId) {
 }
 
 ReturnValue_t StrAssembly::commandChildren(Mode_t mode, Submode_t submode) {
-  commandTable[0].setMode(mode);
+  // To ensure consistent state.
+  commandTable[0].setMode(MODE_OFF);
   commandTable[0].setSubmode(submode);
+  if (healthHelper.healthTable->getHealth(objects::STAR_TRACKER) != FAULTY) {
+    commandTable[0].setMode(mode);
+    commandTable[0].setSubmode(submode);
+  }
   HybridIterator<ModeListEntry> iter(commandTable.begin(), commandTable.end());
   executeTable(iter);
   return returnvalue::OK;