Fix inline test with missing $INCLUDE

The test case for a zone with a missing include file was wrong for two
reasons:
1. It was loading the wrong file (master5 instead of master6)
2. It did actually not set the $ret variable to 1 if the test failed
   (it should default to ret=1 and clear the variable if the
   appropriate log is found).

(cherry picked from commit 96583e7c40)

bin/tests/system/inline/setup.sh

@@ -31,6 +31,7 @@ cp ns3/master.db.in ns3/nsec3.db
 cp ns3/master.db.in ns3/externalkey.db
 cp ns3/master.db.in ns3/delayedkeys.db
 cp ns3/master.db.in ns3/removedkeys-primary.db
+cp ns3/include.db.in ns3/include.db
 
 mkdir ns3/removedkeys