When setting a new default credential in enterprise mode, the code was
only clearing is_default for credentials matching the current user_id.
This caused issues when:
1. Enterprise credential A (synced with system user_id) was default
2. User sets local credential B as default
3. A still had is_default=true (different user_id)
4. Both A and B were considered defaults
The fix removes user_id from the filter only for enterprise deployments,
since enterprise credentials may have different user_id than local ones.
Non-enterprise behavior is unchanged to avoid breaking existing setups.
Fixes EE-1511
53641019b1