Fix bare metal drive cleaning completion flag matching for single-instance platforms. On single-instance platforms, offload services (e.g. `boot_cn_bm_daemon`) and `gbmcweb` create the drive cleaning completion flag without an instance suffix (`/run/bm-drive-cleaning-done.flag`). However, `grpcblobhandler` Instance 0 previously looked strictly for a suffixed flag (`/run/bm-drive-cleaning-done.flag1`), failing to recognize drive cleaning completion and causing host boot to hang in a watchdog reboot loop. Update `baremetal_callback.cc` to fall back to checking the unsuffixed drive cleaning completion flag (`/run/bm-drive-cleaning-done.flag`) if the suffixed flag is not present. This resolves single-instance platform flag detection while keeping `baremetal_callback.h` constructor logic and multi-host instance indexing (`systemdInstanceString`) completely untouched. Tested: Verified via unit tests (`blaze test //third_party/gbmc_grpc_blobs/src/test:baremetal_test`) and live hardware qualification run on host yucbfsr-bct1 (Fusion workflow 8ebeaccd-b4d2-3623-a38c-468bd74298b3: https://fusion2.corp.google.com/8ebeaccd-b4d2-3623-a38c-468bd74298b3). PiperOrigin-RevId: 974747147 Change-Id: I961971e126d9aad1d7eb9929fbc82f3e86458277
TODO(kkachana): Add developer workflow guide
This is a general gRPC blob handler, receives blobs over gRPC and handles accordingly.
SMBIOS gRPC handler receives the SMBIOS from CPU and saves the file at /var/lib/smbios/smbios-remote-host-N and signals smbios app. smbios app parses the saved file and populated smbios objects.