Revert "lakitu: make python3 the default python interpreter"

This reverts commit a723bee6b2b666307595f750e321e914f1e07c10.

Reason for revert: Change the default python interpreter leads to failure of GKE tests. COS should make this change when GKE tests are fixed. Otherwise, dev releases will be blocked.

Original change's description:
> lakitu: make python3 the default python interpreter
> 
> python2 officially is not supported.
> 
> BUG=b:117936434
> TEST=cos_tryjob
> cos_tryjob=https://ci.chromium.org/p/chromeos/builders/general/Try/b8890534654862066576
> RELEASE_NOTE=Made python3 the default python interpreter
> 
> Change-Id: Id70e26daa08bc49a86746eac670175ef563b28c8
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/board-overlays/+/1993641
> Commit-Queue: Roy Yang <royyang@google.com>
> Tested-by: Roy Yang <royyang@google.com>
> Reviewed-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
> Reviewed-by: Xuewei Zhang <xueweiz@google.com>

Bug: b:117936434
Change-Id: I5464a67a79cd55c88d15c8994e17f04687b1c09c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/board-overlays/+/2021836
Tested-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
Tested-by: Roy Yang <royyang@google.com>
Reviewed-by: Roy Yang <royyang@google.com>
Commit-Queue: Roy Yang <royyang@google.com>
diff --git a/overlay-lakitu/scripts/board_specific_setup.sh b/overlay-lakitu/scripts/board_specific_setup.sh
index d634937..969c6cd 100644
--- a/overlay-lakitu/scripts/board_specific_setup.sh
+++ b/overlay-lakitu/scripts/board_specific_setup.sh
@@ -139,4 +139,8 @@
   sudo cp "${script_root}"/dbx/* "${esp_fs_dir}"/efi/Google/GSetup/dbx
   sudo chmod -R 755 "${esp_fs_dir}"/efi/Google/GSetup/dbx
   info "Successfully populated dbx"
+
+  if [[ -e "${root_fs_dir}/usr/bin/python" ]]; then
+    sudo env ROOT="${root_fs_dir}" eselect python set python2.7
+  fi
 }