gitignore: add "*.coverprofile"

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

.gitignore

@@ -9,6 +9,7 @@
 *.log
 /etcd
 /hack/insta-discovery/.env
+*.coverprofile
 *.test
 hack/tls-setup/certs
 .idea