cros_sdk_lib: Make CleanupChrootMount delete consistent.

cros_sdk_lib.CleanupChrootMount has a delete_image option. If
delete_image is True, there is no case where rm'ing the chroot
directory doesn't also make sense, especially since we call this
function for chroots which don't use chroot.img. So... change
'delete_image' to 'delete' and also cleanup the chroot directory.

BUG=None
TEST=run_tests

Change-Id: I845069ab5c5a78e969cafc2b8da168d65dd11b5a
Reviewed-on: https://chromium-review.googlesource.com/1119658
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Jason Clinton <jclinton@chromium.org>
diff --git a/scripts/cros_sdk.py b/scripts/cros_sdk.py
index bf28d96..1e401cb 100644
--- a/scripts/cros_sdk.py
+++ b/scripts/cros_sdk.py
@@ -220,7 +220,7 @@
 
 def CleanupChroot(chroot_path):
   """Unmounts a chroot and cleans up any associated devices."""
-  cros_sdk_lib.CleanupChrootMount(chroot_path, delete_image=False)
+  cros_sdk_lib.CleanupChrootMount(chroot_path, delete=False)
 
 
 def EnterChroot(chroot_path, cache_dir, chrome_root, chrome_root_mount,
@@ -934,8 +934,7 @@
           osutils.UmountTree(options.chroot)
         else:
           logging.notice('Deleting chroot.')
-          cros_sdk_lib.CleanupChrootMount(options.chroot, delete_image=True)
-          osutils.RmDir(options.chroot, ignore_missing=True)
+          cros_sdk_lib.CleanupChrootMount(options.chroot, delete=True)
           chroot_deleted = True
 
   # If cleanup was requested, we have to do it while we're still in the original