Discard PAT for wrong multiplex

When waiting for the PAT for a specific transport stream multiplex
discard PATs for other multiplexes.
After a new tuning request there can be still a number of packets received
from the previous multiplex and these packets can contain a PAT.
This fixes incorrect "Program not found in PAT" and "Rescan your transports"
messages that can sometimes be seen even immediately after a succesful scan.

Refs #13472

mythtv/libs/libmythtv/recorders/dtvsignalmonitor.cpp

@@ -13,7 +13,7 @@ using namespace std;
 
 #undef DBG_SM
 #define DBG_SM(FUNC, MSG) LOG(VB_CHANNEL, LOG_INFO, \
-    QString("DTVSigMon[%1](%2)::%3: %4").arg(m_inputid) \
+    QString("DTVSigMon[%1](%2): %3 %4").arg(m_inputid) \
     .arg(m_channel->GetDevice()).arg(FUNC).arg(MSG))
 
 #define LOC QString("DTVSigMon[%1](%2): ") \
@@ -311,6 +311,14 @@ void DTVSignalMonitor::HandlePAT(const ProgramAssociationTable *pat)
         GetStreamData()->SetVersionPAT(tsid, -1,0);
         // END HACK HACK HACK
 
+        // Discard PAT if we are still on the wrong transport
+        if (m_transportID > 0 && tsid != m_transportID)
+        {
+            DBG_SM("HandlePAT()", QString("Discard PAT for tsid %1 waiting for tsid %2")
+                .arg(tsid).arg(m_transportID));
+            return;
+        }
+
         if (insert_crc(m_seen_table_crc, *pat))
         {
             QString errStr = QString("Program #%1 not found in PAT!")