Return after processing ffdc_only.

If the caller specifies ffdc_only=1, the program should stop after
getting FFDC even if the caller has passed a boot_stack or boot_list.
The name of the parm says it all: ffdc ONLY.

Change-Id: I622ddefb069d24cfca35ae4f32d53e5448b93933
Signed-off-by: Michael Walsh <micwalsh@us.ibm.com>
diff --git a/lib/obmc_boot_test.py b/lib/obmc_boot_test.py
index c90d141..731d233 100755
--- a/lib/obmc_boot_test.py
+++ b/lib/obmc_boot_test.py
@@ -789,6 +789,7 @@
     if ffdc_only:
         gp.qprint_timen("Caller requested ffdc_only.")
         grk.run_key_u("my_ffdc")
+        return
 
     # Process caller's boot_stack.
     while (len(boot_stack) > 0):