Set err in getB2Client

[kula]

vault-plugin-secrets-backblazeb2/plugin/b2_client.go

Lines 52 to 59 in 3e8eb2c

	if c.KeyId == "" {
	b.Logger().Error("KeyID not set when trying to create new client")
	return nil, err
	}
	if c.Key == "" {
	b.Logger().Error("Key not set when trying to create new client")
	return nil, err

At this point, err is still nil, so we won't upstream the errors we're trying to return here.