STORM-1541: Change llassert() to llassert_always(): unit tests expect.

Now that we have unit tests that require assertion failure if you try to
delete an LLInstanceTracker subclass instance with an iterator loose, having
llassert() "sometimes" compile away (whimsically, depending on platform as
well as build type!) makes those tests fail. Use llassert_always() instead.

indra/llcommon/llinstancetracker.h

@@ -197,7 +197,7 @@ class LLInstanceTracker : public LLInstanceTrackerBase
 	virtual ~LLInstanceTracker() 
 	{ 
 		// it's unsafe to delete instances of this type while all instances are being iterated over.
-		llassert(getStatic().sIterationNestDepth == 0);
+		llassert_always(getStatic().sIterationNestDepth == 0);
 		remove_();		
 	}
 	virtual void setKey(KEY key) { remove_(); add_(key); }
@@ -287,7 +287,7 @@ class LLInstanceTracker<T, T*> : public LLInstanceTrackerBase
 	virtual ~LLInstanceTracker()
 	{
 		// it's unsafe to delete instances of this type while all instances are being iterated over.
-		llassert(getStatic().sIterationNestDepth == 0);
+		llassert_always(getStatic().sIterationNestDepth == 0);
 		getSet_().erase(static_cast<T*>(this));
 	}