Update validate_login_vars.yml

Signed-off-by: sakshiarora13 <sakshi_arora1@dell.com>

telemetry/roles/common/tasks/validate_login_vars.yml

@@ -51,6 +51,7 @@
         - '"\\" not in timescaledb_password '
         - '"\"" not in timescaledb_password '
         - " \"'\" not in timescaledb_password "
+        - '"@" not in timescaledb_password '
     no_log: true
 
   - name: Assert mysqldb user name