Fixed and adjusted remainders of isValid() code.

Note that in the code, and still, has_curl_request was always false.
However, instead of deleting all code paths that are only executed
when has_curl_request would be true, I fixed the code to work as
intended with my current implementation; which also results in
LLCurlRequests to never expire. This way things won't break
unexpectedly when this ever changes.

Since on this branch isValid was only called still (the rest was
removed already) to check if the curl download expired, I took
the liberty to rename isValid to hasNotExpired.

indra/llmessage/lliopipe.cpp

@@ -76,7 +76,14 @@ LLIOPipe::~LLIOPipe()
 }
 
 //virtual 
-bool LLIOPipe::isValid() 
+bool LLIOPipe::hasExpiration(void) const
+{
+	// LLIOPipe::hasNotExpired always returns true.
+	return false;
+}
+
+//virtual 
+bool LLIOPipe::hasNotExpired(void) const
 {
 	return true ;
 }