Controller user agent hardcoded to 0.9.7-dev

[jawnsy]

I noticed there's a user agent string which is hard-coded:

gke-autoneg-controller/main.go

Line 43 in b8b9a87

const useragent = "google-pso-tool/gke-autoneg-controller/0.9.7-dev"

[rosmo]

Fixed in 0.9.10.