Fix two critical issues:
1. **Filer Discovery Not Working**: Master client was not being passed to
FilerClient, so peer discovery couldn't work
2. **Credential Store Design**: Already uses FilerClient via GetCurrentFiler
function - this is the correct design for HA
Changes:
**Command (s3.go):**
- Read master addresses from GetFilerConfiguration response
- Pass masterAddresses to S3ApiServerOption
- Log master addresses for visibility
**S3ApiServerOption:**
- Add Masters []pb.ServerAddress field for discovery
**S3ApiServer:**
- Create MasterClient from Masters when available
- Pass MasterClient + FilerGroup to FilerClient via options
- Enable discovery with 5-minute refresh interval
- Log whether discovery is enabled or disabled
**Credential Store:**
- Already correctly uses filerClient.GetCurrentFiler via function
- This provides HA without tight coupling to FilerClient struct
- Function-based design is clean and thread-safe
Discovery Flow:
1. S3 command reads filer config → gets masters + filer group
2. S3ApiServer creates MasterClient from masters
3. FilerClient uses MasterClient to query for peer filers
4. Background goroutine refreshes peer list every 5 minutes
5. Credential store uses GetCurrentFiler to get active filer
Now filer discovery actually works! ��
Chris Lu
af3a0770ff