[fshost] Revert log when encountering unknown disk format

This reverts commit 396d2162.

Reason for revert: we've gotten enough information on the bug that we were trying to investigate with this (DNO-492) that we no longer need this logging, and the excessive logging is causing people grief.

Original change's description:
> [fshost] log when encountering unknown disk format
> 
> DNO-492 #comment
> Tests: paved an Astro, saw this log reasonable content
> for the empty volumes before formatted, did not log after paved.
> 
> Change-Id: I07a80dc2a826e80ba5c12ca5901d460a65266153

TBR=smklein@google.com,abarth@google.com,zarvox@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Ifc296d88a00a9898cebd49980ffcfa409d45b0d0