1. Lazy initialize FilerClient in mount for proxy-only setups
- Only create FilerClient when VolumeServerAccess != "filerProxy"
- Avoids wasted work when all reads proxy through filer
- filerClient is nil for proxy mode, initialized for direct access
2. Fix inaccurate deprecation comment in filer.LookupFn
- Updated comment to reflect current behavior (10k bounded cache)
- Removed claim of "unbounded growth" after adding size limit
- Still directs new code to wdclient.FilerClient for better features
3. Audit all MasterClient usages for KeepConnectedToMaster
- Verified all production callers start KeepConnectedToMaster early
- Filer, Shell, Master, Broker, Benchmark, Admin all correct
- IAM creates MasterClient but never uses it (harmless)
- Test code doesn't need KeepConnectedToMaster (mocks)
All callers properly follow the initialization pattern documented in
GetMaster(), preventing unexpected blocking or timeouts.