Bug 1326653

Upstream "accidentally" fixed this by commit:

commit 466b12ab797f3dc1b37005f5501ebec3549e5cad
Author: Eric Blake <eblake>
Date:   Fri Feb 21 12:55:06 2014 -0700

    virsh: use more compact VIR_ENUM_IMPL
    
    Dan Berrange suggested that using VIR_ENUM_IMPL is more compact
    than open-coding switch statements, and still just as forceful
    at making us remember to update lists if we add enum values
    in the future.  Make this change throughout virsh.
    
    Sure enough, doing this change caught that we missed at least
    VIR_STORAGE_VOL_NETDIR.
    
    * tools/virsh-domain-monitor.c (vshDomainIOErrorToString)
    (vshDomainControlStateToString, vshDomainStateToString)
    (vshDomainStateReasonToString): Change switch to enum lookup.
    (cmdDomControl, cmdDominfo): Update caller.
    * tools/virsh-domain.c (vshDomainVcpuStateToString)
    (vshDomainEventToString, vshDomainEventDetailToString): Change
    switch to enum lookup.
    (vshDomainBlockJobToString, vshDomainJobToString): New functions.
    (cmdVcpuinfo, cmdBlockJob, cmdDomjobinfo, cmdEvent): Update
    callers.
    * tools/virsh-network.c (vshNetworkEventToString): Change switch
    to enum lookup.
    * tools/virsh-pool.c (vshStoragePoolStateToString): New function.
    (cmdPoolList, cmdPoolInfo): Update callers.
    * tools/virsh-volume.c (vshVolumeTypeToString): Change switch to
    enum lookup.
    (cmdVolInfo, cmdVolList): Update callers.
    
    Signed-off-by: Eric Blake <eblake>

Verify it on libvirt-0.10.2-62.el6.x86_64
1. Prepare a running VM b1
2. Runing following script reproduce.sh
```
#!/bin/bash
DOM=b1
DOM_IP=192.168.122.86

for i in s{1..3};do
    virsh snapshot-create-as $DOM $i --no-metadata --disk-only
    ssh root@$DOM_IP dd if=/dev/urandom of=hello bs=1k count=102400
done
qemu-img info /var/lib/libvirt/images/$DOM.s3  --backing-chain
virsh blockcommit $DOM hda --top /var/lib/libvirt/images/$DOM.s1
for i in {1..10};do
    virsh blockjob $DOM hda
done 

```
3. Check the result
Domain snapshot s1 created
102400+0 records in
102400+0 records out
104857600 bytes (105 MB) copied, 19.0657 s, 5.5 MB/s
Domain snapshot s2 created
102400+0 records in
102400+0 records out
104857600 bytes (105 MB) copied, 18.5078 s, 5.7 MB/s
Domain snapshot s3 created
102400+0 records in
102400+0 records out
104857600 bytes (105 MB) copied, 18.7518 s, 5.6 MB/s
image: /var/lib/libvirt/images/b1.s3
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 98M
cluster_size: 65536
backing file: /var/lib/libvirt/images/b1.s2
backing file format: qcow2

image: /var/lib/libvirt/images/b1.s2
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 101M
cluster_size: 65536
backing file: /var/lib/libvirt/images/b1.s1
backing file format: qcow2

image: /var/lib/libvirt/images/b1.s1
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 94M
cluster_size: 65536
backing file: /var/lib/libvirt/images/b1.qcow2
backing file format: qcow2

image: /var/lib/libvirt/images/b1.qcow2
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 1.2G
cluster_size: 65536
Block Commit started
Block Commit: [ 44 %]
Block Commit: [ 48 %]
Block Commit: [ 48 %]
Block Commit: [ 49 %]
Block Commit: [ 49 %]
Block Commit: [ 49 %]
Block Commit: [ 49 %]
Block Commit: [ 49 %]
Block Commit: [ 49 %]
Block Commit: [ 49 %]


No 'unknown job' when blockcommit. Bug fixed.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2017-0682.html