shutdown: Conditionally unmount proc

The intention was to test the flag variable set when proc was
mounted earlier in the script, not the constant string containing
the name of the variable.

The unnecessary unmount is not noticeable when a normal shutdown
or reboot is being performed while executing after systemd, but
results in a less usable environment when invoked manually.

Signed-off-by: Milton Miller <miltonm@us.ibm.com>
diff --git a/meta-phosphor/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh b/meta-phosphor/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh
index fc359c5..216e7e4 100644
--- a/meta-phosphor/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh
+++ b/meta-phosphor/common/recipes-phosphor/obmc-phosphor-initfs/files/obmc-shutdown.sh
@@ -45,7 +45,7 @@
 echo Remaining mounts:
 cat /proc/mounts
 
-test "umount_proc" && umount /proc && rmdir /proc
+test "$umount_proc" && umount /proc && rmdir /proc
 
 # ioctl(TIOC_DRAIN) to drain tty messages to console
 test -t 1 && stty cooked 0<&1