[blobfs][test] Actually apply journal in blobfs journaling tests

Two minor changes to the execution of:
  /boot/test/blobfs-test -f 0

Which runs all blobfs tests, but halts execution after writing
1, 2, 3, ... blocks.

- Since we are checking the consistency via fsck, apply the journal
before this validation. Otherwise, these tests fail almost immediately.
- Actually halt the test if filesystem corruption is detected.

ZX-3956 #comment In Progress

Change-Id: Ia663d3c71348cdd1a1b75207370ec2846c00f0da