Fixes typos for adb shell stop/start.

Test: n/a
Change-Id: Idaad0bfbf3c9d3fd7fc768940746c78528116a13
diff --git a/fs_mgr/README.overlayfs.md b/fs_mgr/README.overlayfs.md
index bb63df8..f579078 100644
--- a/fs_mgr/README.overlayfs.md
+++ b/fs_mgr/README.overlayfs.md
@@ -32,9 +32,9 @@
 
 Then enter one of the following sequences:
 
-    $ adb stop
+    $ adb shell stop
     $ adb sync
-    $ adb start
+    $ adb shell start
     $ adb reboot
 
 *or*