shutdown: Test equality with =

The test command is documented as taking = and not == to test
two strings for equality.  While both appear to work use the
documented comparison operator.

Signed-off-by: Milton Miller <miltonm@us.ibm.com>
diff --git a/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh b/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh
index 097d9e0..99a7432 100644
--- a/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh
+++ b/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh
@@ -53,7 +53,7 @@
 # Execute the command systemd told us to ...
 if test -d /oldroot  && test "$1"
 then
-	if test "$1" == kexec
+	if test "$1" = kexec
 	then
 		$1 -f -e
 	else