bitbake: toaster: unset environment variables

Toaster script sets environment variables when it starts.
It makes sense to unset them when toaster stops as they can
cause other programs to behave incorrectly.

(Bitbake rev: 7a2e9745ff3ef6d6360f74b222248d4bd35e6a08)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: brian avery <avery.brian@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/bin/toaster

@@ -128,6 +128,10 @@ stop_system()
     fi
     stop_bitbake
     webserverKillAll
+    # unset exported variables
+    unset DATABASE_URL
+    unset TOASTER_CONF
+    unset TOASTER_DIR
     trap - SIGHUP
     #trap - SIGCHLD
     INSTOPSYSTEM=0