move SQL-based pool functionality to new attr-sql libstrongswan plugin

testing/tests/sql/ip-split-pools-db-restart/hosts/moon/etc/strongswan.conf

@@ -6,7 +6,15 @@ charon {
       database = sqlite:///etc/ipsec.d/ipsec.db 
     }
   }
-  load = curl aes des sha1 sha2 md5 pem pkcs1 gmp random x509 hmac xcbc stroke kernel-netlink updown sqlite sql
+  load = curl aes des sha1 sha2 md5 pem pkcs1 gmp random x509 hmac xcbc stroke kernel-netlink updown sqlite sql attr-sql
+}
+
+libstrongswan {
+  plugins {
+    attr-sql {
+      database = sqlite:///etc/ipsec.d/ipsec.db
+    }
+  }
 }
 
 pool {