The filesystem store driver in glance_store does not have any timeouts for filesystem operations. When storage becomes unavailable, operations like os.path.exists(), os.unlink(), and os.statvfs() can hang forever. This causes Glance API timeouts and bad user experience.

Common scenarios where these problems happen:

• NFS server outages or network problems
• Storage backend failures (PowerFlex, PowerStore, etc.)
• Network connectivity issues between Glance and storage
• Storage maintenance windows
• Local disk failures that cause IO operations to hang

When these problems happen, Glance operations like image deletion, retrieval, and storage capacity checks will hang forever. This causes:

• API timeouts and bad user experience
• Resource exhaustion on Glance API servers
• Cannot perform maintenance operations
• Cascading failures in OpenStack deployments

Add timeout protection to the filesystem driver. This prevents operations from hanging forever. This keeps backward compatibility by default. Default is blocking IO (timeout = 0 means wait forever).