[__letsencrypt_cert] Simplify derivation of python path.

This also supports odd setups with '!' in the path.

cdist/conf/type/__letsencrypt_cert/explorer/certificate-data

@@ -6,7 +6,7 @@ certificate_is_test="no"
 
 if [ -n "${certbot_path}" ]; then
 	# Find python executable that has access to certbot's module
-	python_path="$(head -n 1 "${certbot_path}" | cut -d '!' -f 2)"
+	python_path=$(sed -n '1s/^#! *//p' "${certbot_path}")
 
 	# Use a lock for cdist due to certbot not exiting with failure
 	# or having any flags for concurrent use.