The Nova extension API was deprecated from OpenStack N release.
this parts of code cannot work well with the newest OpenStack version.
This patch is to remove the relative parts:
1. Remove the step_load_extensions.go
2. Remove the step of extension from builder.go
3. Remove the parameter parsing from step_stop_server.go
Resolves: #5581
Run now takes a context as well as a statebag. We'll assign the context
to the blank identifier to prevent namespace collisions. We'll let the
step authors opt-in to using the context.
`find . -iname "step_*.go" -exec gsed -i'' 's/func \(.*\)Run(/func \1Run(_ context.Context, /' {} \;`