pcbnew: Do not allow drag to violate DRC without permission

m_dragstatus is set to true when a valid route is created given the
user's constraints.  We need to check this before committing the route
to the board.

Fixes: lp:1794810
* https://bugs.launchpad.net/kicad/+bug/1794810

(cherry picked from commit 317ca8e64d)

pcbnew/router/pns_dragger.cpp

@@ -323,6 +323,10 @@ bool DRAGGER::FixRoute()
 
     if( node )
     {
+        // Collisions still prevent fixing unless "Allow DRC violations" is checked
+        if( !m_dragStatus )
+            return false;
+
         Router()->CommitRouting( node );
         return true;
     }