fix(cert-gen.sh.j2): fix salt-lint errors

```bash
Examining vault/files/cert-gen.sh.j2 of type state
[204] Lines should be no longer that 160 chars
vault/files/cert-gen.sh.j2:34
root_subj="/C={{ vault.self_signed_cert.country }}/ST={{ vault.self_signed_cert.state }}/L={{ vault.self_signed_cert.city }}/O={{ vault.self_signed_cert.org }}/OU={{ vault.self_signed_cert.org_unit }}/CN=$root\_ca"

[204] Lines should be no longer that 160 chars
vault/files/cert-gen.sh.j2:75
child_subj="/C={{ vault.self_signed_cert.country }}/ST={{ vault.self_signed_cert.state }}/L={{ vault.self_signed_cert.city }}/O={{ vault.self_signed_cert.org }}/OU={{ vault.self_signed_cert.org_unit }}/CN=$child_name"
```

vault/files/cert-gen.sh.j2

@@ -1,4 +1,5 @@
 {% from "vault/map.jinja" import vault with context -%}
+{% set vssc = vault.self_signed_cert -%}
 #!/usr/bin/env bash
 
 ###
@@ -31,7 +32,7 @@ pw="$child"
 root_key="$root.key"
 root_pem="$root.pem"
 root_key_nopass="$root-nopass.key"
-root_subj="/C={{ vault.self_signed_cert.country }}/ST={{ vault.self_signed_cert.state }}/L={{ vault.self_signed_cert.city }}/O={{ vault.self_signed_cert.org }}/OU={{ vault.self_signed_cert.org_unit }}/CN=$root\_ca"
+root_subj="/C={{ vssc.country }}/ST={{ vssc.state }}/L={{ vssc.city }}/O={{ vssc.org }}/OU={{ vssc.org_unit }}/CN=$root\_ca"
 root_p12="$root.p12"
 
 ###
@@ -72,7 +73,7 @@ child_name="${root}_${child}"
 child_key="$child_name.key"
 child_pem="$child_name.pem"
 child_csr="$child_name.csr"
-child_subj="/C={{ vault.self_signed_cert.country }}/ST={{ vault.self_signed_cert.state }}/L={{ vault.self_signed_cert.city }}/O={{ vault.self_signed_cert.org }}/OU={{ vault.self_signed_cert.org_unit }}/CN=$child_name"
+child_subj="/C={{ vssc.country }}/ST={{ vssc.state }}/L={{ vssc.city }}/O={{ vssc.org }}/OU={{ vssc.org_unit }}/CN=$child_name"
 child_p12="$child_name.p12"
 child_jks="$child_name.jks"