Improves error reporting for vSphere stemcell creation [Finishes #61155578]

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>
Improves error reporting during vSphere VM power on.

Also, bails if any recommendations are detected, as this implies that
DRS is in manual mode (which we don't want as it leads to unrespondable
questions being sent to the client).

[Finishes #61155578]

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>