This patch removes mount.Exec entirely and instead uses the common
utility from k8s.io/utils/exec.
The fake exec implementation found in k8s.io/utils/exec differs a bit
than mount.Exec, with the ability to pre-script expected calls to
Command.CombinedOutput(), so tests that previously relied on a callback
mechanism to produce specific output have been updated to use that
mechanism.
This prepares volume plugins to run things in containers instead of running
them on the host.
As consequence, a mount.Exec interface needs to be passed from VolumeHost
down to SioClient.
This commit introduces the following updates and fixes:
- Enable scaleIO volume multip-mapping based on accessMode
- No longer uses "default" as default values for storagepool & protection domain
- validates capacity when capacity is zero
- Better naming for PV and volume
- make mount ro when accessModes contains ROM
