Bump go-discover to fix broken dep (hashicorp#12404)

The previous version of `go-discover` pulled in a broken version of
`tencentcloud-sdk-go`, resulting in anything that runs `go get -d`
downstream breaking... ie, a dep on hashicorp vault will break
Dependabot (among other things).

I already fixed it in `go-discover`, so this just pulls in the update.

More details in
hashicorp/go-discover@657e803
and hashicorp/go-discover#172.

go.mod

@@ -59,7 +59,7 @@ require (
 	github.com/hashicorp/consul/api v1.4.0
 	github.com/hashicorp/errwrap v1.1.0
 	github.com/hashicorp/go-cleanhttp v0.5.2
-	github.com/hashicorp/go-discover v0.0.0-20201029210230-738cb3105cd0
+	github.com/hashicorp/go-discover v0.0.0-20210818145131-c573d69da192
 	github.com/hashicorp/go-gcp-common v0.7.0
 	github.com/hashicorp/go-hclog v0.16.2
 	github.com/hashicorp/go-kms-wrapping v0.6.4

go.sum

@@ -596,8 +596,8 @@ github.com/hashicorp/go-cleanhttp v0.5.0/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtng
 github.com/hashicorp/go-cleanhttp v0.5.1/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
 github.com/hashicorp/go-cleanhttp v0.5.2 h1:035FKYIWjmULyFRBKPs8TBQoi0x6d9G4xc9neXJWAZQ=
 github.com/hashicorp/go-cleanhttp v0.5.2/go.mod h1:kO/YDlP8L1346E6Sodw+PrpBSV4/SoxCXGY6BqNFT48=
-github.com/hashicorp/go-discover v0.0.0-20201029210230-738cb3105cd0 h1:UgODETBAoROFMSSVgg0v8vVpD9Tol8FtYcAeomcWJtY=
-github.com/hashicorp/go-discover v0.0.0-20201029210230-738cb3105cd0/go.mod h1:D4eo8/CN92vm9/9UDG+ldX1/fMFa4kpl8qzyTolus8o=
+github.com/hashicorp/go-discover v0.0.0-20210818145131-c573d69da192 h1:eje2KOX8Sf7aYPiAsLnpWdAIrGRMcpFjN/Go/Exb7Zo=
+github.com/hashicorp/go-discover v0.0.0-20210818145131-c573d69da192/go.mod h1:3/4dzY4lR1Hzt9bBqMhBzG7lngZ0GKx/nL6G/ad62wE=
 github.com/hashicorp/go-gatedio v0.5.0 h1:Jm1X5yP4yCqqWj5L1TgW7iZwCVPGtVc+mro5r/XX7Tg=
 github.com/hashicorp/go-gatedio v0.5.0/go.mod h1:Lr3t8L6IyxD3DAeaUxGcgl2JnRUpWMCsmBl4Omu/2t4=
 github.com/hashicorp/go-gcp-common v0.5.0/go.mod h1:IDGUI2N/OS3PiU4qZcXJeWKPI6O/9Y8hOrbSiMcqyYw=
@@ -1214,7 +1214,6 @@ github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/svanharmelen/jsonapi v0.0.0-20180618144545-0c0828c3f16d h1:Z4EH+5EffvBEhh37F0C0DnpklTMh00JOkjW5zK3ofBI=
 github.com/svanharmelen/jsonapi v0.0.0-20180618144545-0c0828c3f16d/go.mod h1:BSTlc8jOjh0niykqEGVXOLXdi9o0r0kR8tCYiMvjFgw=
 github.com/tencentcloud/tencentcloud-sdk-go v1.0.162/go.mod h1:asUz5BPXxgoPGaRgZaVm1iGcUAuHyYUo1nXqKa83cvI=
-github.com/tencentcloud/tencentcloud-sdk-go v3.0.83+incompatible/go.mod h1:0PfYow01SHPMhKY31xa+EFz2RStxIqj6JFAJS+IkCi4=
 github.com/tencentcloud/tencentcloud-sdk-go v3.0.171+incompatible h1:K3fcS92NS8cRntIdu8Uqy2ZSePvX73nNhOkKuPGJLXQ=
 github.com/tencentcloud/tencentcloud-sdk-go v3.0.171+incompatible/go.mod h1:0PfYow01SHPMhKY31xa+EFz2RStxIqj6JFAJS+IkCi4=
 github.com/tidwall/pretty v1.0.0/go.mod h1:XNkn88O1ChpSDQmQeStsy+sBenx6DDtFZJxhVysOjyk=