qemuDomainNestedJobAllowed: Allow QEMU_JOB_NONE
qemuDomainNestedJobAllowed: Allow QEMU_JOB_NONE

https://bugzilla.redhat.com/show_bug.cgi?id=1598084

When creating a snapshot with --quiesce an async job is grabbed
and just before executing guest fs-freeze command an agent job is
grabbed. This is achieved by calling

  qemuDomainObjBeginJobInternal(job = QEMU_JOB_NONE,
                                agentJob = QEMU_AGENT_JOB_MODIFY);

Since there already is an async job set on the domain (by the
same thread) qemuDomainNestedJobAllowed(priv, job) is consulted
if @job is allowed by job mask. But this function returns false
(meaning sync @job is not allowed) which leads to a deadlock.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>
Reviewed-by: Jiri Denemark <62bdf77dc47919a4d59a91822129d14633cfca81@redhat.com>

andreabolognani/libvirt,eskultety/libvirt,nertpinx/libvirt,zippy2/libvirt,nertpinx/libvirt,libvirt/libvirt,eskultety/libvirt,jfehlig/libvirt,nertpinx/libvirt,andreabolognani/libvirt,zippy2/libvirt,crobinso/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,libvirt/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,nertpinx/libvirt,andreabolognani/libvirt,zippy2/libvirt,andreabolognani/libvirt,olafhering/libvirt,zippy2/libvirt,crobinso/libvirt,olafhering/libvirt,libvirt/libvirt,jfehlig/libvirt,libvirt/libvirt,jfehlig/libvirt,crobinso/libvirt,andreabolognani/libvirt,crobinso/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,olafhering/libvirt,eskultety/libvirt,eskultety/libvirt,eskultety/libvirt,jardasgit/libvirt,jardasgit/libvirt,olafhering/libvirt