Merge remote-tracking branch 'mreitz/tags/pull-block-2018-11-12' into queue-block

Block patches:
- Added NULL checks found by static analysis
- Allow more block drivers to not be included in the qemu build

# gpg: Signature made Mon Nov 12 17:51:18 2018 CET
# gpg:                using RSA key F407DB0061D5CF40
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>"
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* mreitz/tags/pull-block-2018-11-12:
  qcow2: Read outside array bounds in qcow2_pre_write_overlap_check()
  block: Fix potential Null pointer dereferences in vvfat.c
  qemu-img: assert block_job_get() does not return NULL in img_commit()
  block: Null pointer dereference in blk_root_get_parent_desc()
  job: Fix off-by-one assert checks for JobSTT and JobVerbTable
  block: Make more block drivers compile-time configurable

Signed-off-by: Kevin Wolf <kwolf@redhat.com>