cli: CEPH_ARGS must be before injectargs

It is incorrect to append the content of CEPH_ARGS to the argument list
when running injectargs. For instance if

  CEPH_ARGS='--log-file the.log' \
    ./ceph tell osd.0 injectargs --no-osd_debug_op_order

translates into

    ./ceph tell osd.0 injectargs --no-osd_debug_op_order \
                                 --log-file the.log

it ends up changing the log file of osd.0 which is probably unintended.
Instead CEPH_ARGS is inserted before injectargs and it translates into:

    ./ceph tell osd.0 --log-file the.log \
                      injectargs --no-osd_debug_op_order

Signed-off-by: Loic Dachary <loic-201408@dachary.org>