qemuDomainObjBeginJobInternal: Return -2 for temporary failures
qemuDomainObjBeginJobInternal: Return -2 for temporary failures

If job queue is full or waiting for a job times out, the function
returns -2 so that it can be handled in a different way by callers.

All callers are updated (when necessary) to only check for the return
value to be less than zero.

https://bugzilla.redhat.com/show_bug.cgi?id=1083238
https://bugzilla.redhat.com/show_bug.cgi?id=1100671

Signed-off-by: Jiri Denemark <62bdf77dc47919a4d59a91822129d14633cfca81@redhat.com>
(cherry picked from commit dca377dbd63a514963a06f4f15aa61fb8cb7f19b)
Signed-off-by: Jiri Denemark <62bdf77dc47919a4d59a91822129d14633cfca81@redhat.com>

Conflicts:
	src/qemu/qemu_domain.c -- missing b090aa7d5; old spelling of
	    maxQueuedJobs

Downstream changes:
    - qemuDomainObjBeginNestedJob is inlined in
      qemuDomainObjBeginJobInternal
    - more callers of qemuDomainObjBeginJobInternal had to be fixed

(cherry picked from 6.6 commit ddb80312b6eaea5248c18a2b03814aa251472165)
Signed-off-by: Jiri Denemark <62bdf77dc47919a4d59a91822129d14633cfca81@redhat.com>

mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2