Typo in oracle version check
Motivation
----------
The check for the oracle version needed for the generic meta data has a typo in calling the connection function [here](https://github.com/rucio/rucio/blob/master/lib/rucio/core/did.py#L1291)

Modification
------------
```
session.connection().connection
```
instead of 
```
session.connection.connection
```

diff --git a/lib/rucio/core/did.py b/lib/rucio/core/did.py
index 5e46a7887..94ef52408 100644
--- a/lib/rucio/core/did.py
+++ b/lib/rucio/core/did.py
@@ -1288,7 +1288,7 @@ def get_did_meta(scope, name, session=None):
     :param name: the name of the did
     """
     if session.bind.dialect.name == 'oracle':
-        oracle_version = int(session.connection.connection.version.split('.')[0])
+        oracle_version = int(session.connection().connection.version.split('.')[0])
         if oracle_version < 12:
             raise NotImplementedError
 
['lib/rucio/core/did.py']