Move execution of qrexec_agent to qubes_core

Previously it was in both qubes_core_appvm and qubes_core_netvm;
somehow counterintuitively, qubes_core_netvm executes on appvm, too. So
move it to a common place.

appvm/qubes_core_appvm

@@ -55,7 +55,6 @@ start()
     MEM_CHANGE_THRESHOLD_KB=30000
     MEMINFO_DELAY_USEC=100000
     /usr/lib/qubes/meminfo-writer $MEM_CHANGE_THRESHOLD_KB $MEMINFO_DELAY_USEC &
-    /usr/lib/qubes/qrexec_agent 2>/var/log/qubes/qrexec_agent.log &
 
 	success
 	echo ""

common/qubes_core

@@ -54,6 +54,8 @@ start()
         fi
 	fi
 
+	/usr/lib/qubes/qrexec_agent 2>/var/log/qubes/qrexec_agent.log &
+
 	[ -x /rw/config/rc.local ] && /rw/config/rc.local
 	success
 	echo ""

netvm/qubes_core_netvm

@@ -32,7 +32,6 @@ start()
 		/usr/lib/qubes/qubes_setup_dnat_to_ns
 		echo "1" > /proc/sys/net/ipv4/ip_forward
 	fi
-	/usr/lib/qubes/qrexec_agent 2>/var/log/qubes/qrexec_agent.log &
 	
 	success
 	echo ""