CASMPET-5266: Bump go version to 1.17.6

The build doesn't work with go version 1.16.9. The build was failing
with

```
[2022-01-25T22:54:22.534Z] vendor/sigs.k8s.io/json/internal/golang/encoding/json/encode.go:1249:12: sf.IsExported undefined (type reflect.StructField has no field or method IsExported)
```

Looking at bugs like kubernetes-sigs/json#8
it says that go 1.16 is on its way out.

The latest 1.17 is 1.17.6, see
https://go.dev/doc/devel/release#go1.17.minor

buildPrep.sh

@@ -22,7 +22,7 @@ else
   tar -C /usr/local -xzf go1.16.9.linux-amd64.tar.gz
 fi
 
-GO_VERSION="1.16.9"
+GO_VERSION="1.17.6"
 INSTALLED_GO_VERSION=$(go version | awk '{print $3}')
 
 if [[ "go${GO_VERSION}" !=  $INSTALLED_GO_VERSION ]]; then