Revert "test_filejournal.cc: cleanup memory in destructor"

The finish() method for Contexts calls delete this.

This reverts commit 36028916c4630ea66007760efed8fc6c441e7af5.

Fixes: #5075
Signed-off-by: Samuel Just <sam.just@inktank.com>
Reviewed-by: David Zafman <david.zafman@inktank.com>
test_filestore_idempotent_sequence: unmount prior to deleting store

FileStoreDiff umounts the stores in its destructor.

Also, DeterministicOpSequence handles deletes its passed
object store.

Fixes: #5076
Signed-off-by: Samuel Just <sam.just@inktank.com>
Reviewed-by: David Zafman <david.zafman@inktank.com>