Add docstrings for parameter translation

On some APIs, the argument disk_config is translated to
OS-DCF:diskConfig as the parameter name. So this patch
adds docstrings for explaing it. In addition, this replaces
del with dict.pop() for code cleanup.

Partially implements blueprint consistent-service-method-names

Change-Id: If24590632b984b6ba35477027fcd6a5e40a9335a
1 file changed