test: don't leak agent goroutines in TestAgent_sidecarServiceFromNodeService (#6396)
test: don't leak agent goroutines in TestAgent_sidecarServiceFromNodeService (#6396)

A goroutine dump using runtime.Stack() before/after shows a drop from 121 => 4.
scalp42/consul,42wim/consul,kingland/consul,kingland/consul,42wim/consul,hashicorp/consul,hashicorp/consul,kingland/consul,kingland/consul,hashicorp/consul,42wim/consul,scalp42/consul,scalp42/consul,scalp42/consul,hashicorp/consul,42wim/consul,42wim/consul,kingland/consul,scalp42/consul