fixed tencentcloud tag

[likexian]

This PR only fix the tag of tencentcloud.
I have test it and passed.

go test -v
=== RUN   TestAddrs
2021/08/23 12:48:12 [DEBUG] discover-tencentcloud: Using region=ap-guangzhou, tag_key=consul, tag_value=test
2021/08/23 12:48:12 [DEBUG] discover-tencentcloud: Static credentials provided
2021/08/23 12:48:12 [DEBUG] discover-tencentcloud: region is ap-guangzhou
2021/08/23 12:48:12 [DEBUG] discover-tencentcloud: address type is private_v4
2021/08/23 12:48:12 [DEBUG] discover-tencentcloud: Filter instances with consul=test
2021/08/23 12:48:17 [DEBUG] discover-tencentcloud: Found 2 instances
2021/08/23 12:48:17 [DEBUG] discover-tencentcloud: Instance ins-xxxfu has private_v4 10.1.2.1
2021/08/23 12:48:17 [DEBUG] discover-tencentcloud: Instance ins-xxxbu has private_v4 10.1.2.2
2021/08/23 12:48:17 [DEBUG] discover-tencentcloud: Found address: [10.1.2.1 10.1.2.2]
--- PASS: TestAddrs (5.12s)
PASS
ok      github.com/hashicorp/go-discover/provider/tencentcloud  5.136s

[hashicorp-cla]

All committers have signed the CLA.