Updates hydra: a4f5dff Fix: provision: grub: on efibootmgr

diff --git a/hydra b/hydra
index 5d8c13e99c6112f445659bda803f0d86c1e642bb..a4f5dffc79b784d2986a2075dc4a8b1062ab6f50 160000 (submodule)
--- a/hydra
+++ b/hydra
@@ -1 +1 @@
-Subproject commit 5d8c13e99c6112f445659bda803f0d86c1e642bb
+Subproject commit a4f5dffc79b784d2986a2075dc4a8b1062ab6f50