[SMAPIv3] Error accessing device in xe vbd-plug leaves device "half plugged"

[ydirson]

Not sure of the situations where this can happen aside from testing a nt-fully-implemented SR driver, but it seems that a failure to plug a VBD for whatever reason should not result in it staying plugged.

Test with wrong mapping of VDI to blockdev:

[18:12 xcpng83-bzkcpvhy ~]# xe vbd-plug uuid=01ac1ee8-7b8e-dc4a-32bc-cdfaa2030fc2
There was an SR backend failure.
status: OSError
stdout: [Errno 2] No such file or directory: '///var/run/sr-mount/sr-aebf3312-79bf-cd2e-6ae6-fed601255f35/2'
stderr: <unknown>

Then after fixing the problem, we have to unplug first that VBD that failed to plug:

[18:12 xcpng83-bzkcpvhy ~]# xe vbd-plug uuid=01ac1ee8-7b8e-dc4a-32bc-cdfaa2030fc2 
The device is already attached to a VM
device: 01ac1ee8-7b8e-dc4a-32bc-cdfaa2030fc2
[18:16 xcpng83-bzkcpvhy ~]# xe vbd-unplug uuid=01ac1ee8-7b8e-dc4a-32bc-cdfaa2030fc2 
[18:16 xcpng83-bzkcpvhy ~]# xe vbd-plug uuid=01ac1ee8-7b8e-dc4a-32bc-cdfaa2030fc2 
[18:16 xcpng83-bzkcpvhy ~]#