Adding HA support for Keystone charm

Change-Id: I691154ef2952bc124d7ddb689e39455c213c2a4b
Signed-off-by: sousaedu <eduardo.sousa@canonical.com>
diff --git a/installers/charm/keystone/config.yaml b/installers/charm/keystone/config.yaml
index b014e55..1ad4785 100644
--- a/installers/charm/keystone/config.yaml
+++ b/installers/charm/keystone/config.yaml
@@ -93,6 +93,10 @@
     description: |
       Project domain name (Hardcoded in the container start.sh script)
     default: default
+  token_expiration:
+    type: int
+    description: Token keys expiration in seconds
+    default: 172800
   ldap_enabled:
     type: boolean
     description: Boolean to enable/disable LDAP authentication