storage#DeleteBlobIfExists: fix panic if resp==nil (#444)
storage#DeleteBlobIfExists: fix panic if resp==nil (#444)

A resp.body.Close() statement was causing nil pointer dereference
panics when deleteBlob() returned an error and hence resp was nil.

Signed-off-by: Ahmet Alp Balkan <787aefc6cbd2e3e8663c1f03b44afee9126bfa5e@gmail.com>
marstr/azure-sdk-for-go,curoverse/azure-sdk-for-go,stubey/azure-sdk-for-go,curoverse/azure-sdk-for-go,colemickens/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,lirao/azure-sdk-for-go,marstr/azure-sdk-for-go,marstr/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,stubey/azure-sdk-for-go,lirao/azure-sdk-for-go