cmd/upspin-setupstorage-drive: Change backend config value to match the registered value

The backend config value "Drive" is used for registration but
"drive" is used in setupstorage.

upspin/upspin#569

Change-Id: I365cf65dc419b089cef6510e4c951aad41b2dadb
Reviewed-on: https://upspin-review.googlesource.com/18220
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/cmd/upspin-setupstorage-drive/setupstorage.go b/cmd/upspin-setupstorage-drive/setupstorage.go
index 95dcfe2..6da9f40 100644
--- a/cmd/upspin-setupstorage-drive/setupstorage.go
+++ b/cmd/upspin-setupstorage-drive/setupstorage.go
@@ -58,7 +58,7 @@
 	cfgPath := filepath.Join(*where, *domain)
 	cfg := s.ReadServerConfig(cfgPath)
 	cfg.StoreConfig = []string{
-		"backend=drive",
+		"backend=Drive",
 		"accessToken=" + tok.AccessToken,
 		"tokenType=" + tok.TokenType,
 		"refreshToken=" + tok.RefreshToken,