services/obs: Obs does not support read with size and offset

[Joey2132]

Currently obs does not support read with size and offset. When I migrate to Factory init, the integration test requires that TestReadWithOffset item status should be pass. Before I migrate issue #1022, which I should choose?

1. Ignore read operation
2. Hang up the migration of obs

[Xuanwo]

I think we can mark read as not supported for now.

[Joey2132]

Got it.