settings: FCB back-end does not try to add record after the last compression attempt.

[nvlsianpu]

bug description
sttings key-value pair write request has build in GC mechanism called compression.
settings FCB back-end doesn't try to add record after the last compression attempt.
This imposes that it might be impossible to write key-value pair even that there is a room for it after back-end GC.

If the last compression made a room then subsequent write request might be successfully.

Expected behavior
possible to write if there is a room made within same write request which performs the compression.

Impact
Key-value pair might be not written despite the fact that there is room for it.