Incorrect call set_exit_wait_early_message

obmc_boot_test.py function stop_boot_test was incorrectly calling
set_wait_early_exit_message.  The correct name is set_exit_wait_early_message.

Change-Id: Ie1ce60f3e32261af43b3ccf274251f27198996b0
Signed-off-by: Michael Walsh <micwalsh@us.ibm.com>
diff --git a/lib/obmc_boot_test.py b/lib/obmc_boot_test.py
index e864571..07bbc58 100755
--- a/lib/obmc_boot_test.py
+++ b/lib/obmc_boot_test.py
@@ -810,7 +810,7 @@
 
     function_stack = gm.get_function_stack()
     if "wait_state" in function_stack:
-        st.set_wait_early_exit_message(message)
+        st.set_exit_wait_early_message(message)
     else:
         BuiltIn().fail(gp.sprint_error(message))