AMI: Fix stage2 builds

I got rid of all the sudos in nix-provision.sh thinking it was being run
like stage1 and did not notice before auto-merge did its thing. This
fixes the builds.

Author: mmlb

stage2-nix-psql.pkr.hcl

@@ -128,7 +128,8 @@ build {
       "GIT_SHA=${var.git_sha}",
       "POSTGRES_MAJOR_VERSION=${var.postgres_major_version}"
     ]
-    script = "ebssurrogate/scripts/nix-provision.sh"
+    use_env_var_file = true
+    script           = "ebssurrogate/scripts/nix-provision.sh"
+    execute_command  = "sudo -S sh -c '. {{.EnvVarFile}} && cd /tmp/ansible-playbook && {{.Path}}'"
   }
-
 }