runsc: fsgofer should return a unique QID.Path for each file.
runsc: fsgofer should return a unique QID.Path for each file.

Previously, we were only using the host inode id as the QID path. But the host
filesystem can have multiple devices with conflicting inode ids. This resulted
in duplicate inode ids in the sentry.

This CL generates a unique QID for each <host inode, host device> pair.

PiperOrigin-RevId: 210424813
Change-Id: I16d106f61c7c8f910c0da4ceec562a010ffca2fb

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor