test/osd/osd-scrub-repair.sh: Adjust for FreeBSD

test/osd/osd-scrub-repair.sh: Adjust for FreeBSD

Fixes 2 problems:
 -  Do not test Bluestore on FreeBSD, since that does not work (yet)
    And all erasure code overwrite tests are executed on BlueStore OSDs
    Erasure code overwrites are unsafe on Filestore, see:
    http://docs.ceph.com/docs/master/rados/operations/erasure-code/#erasure-coding-with-overwrites

 -  the JQ expression errors out with:
    (version 1.5-1-g940132e-dirty)
    ====
    jq: error (at :232): Cannot iterate over null (null)
    Traceback (most recent call last):
    File "", line 1, in
    File "/usr/lib64/python2.7/json/init.py", line 338, in loads
    return _default_decoder.decode(s)
    File "/usr/lib64/python2.7/json/decoder.py", line 365, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
    File "/usr/lib64/python2.7/json/decoder.py", line 383, in raw_decode
    raise ValueError("No JSON object could be decoded")
    ValueError: No JSON object could be decoded
    ====
    Adding a ? to the jq expression allows to proceed on null blocks.

Signed-off-by: Willem Jan Withagen <wjw@digiware.nl>