Add signal to the im test group (#259)

* Add signal to the im test group

* fix(ipconfig_test.go): disable when running in CI

Reference issue: https://github.com/ooni/probe/issues/1418

* fix(geolocate): remove unused variable

Came across this while looking into this issue with the CI that
is now failing. Guess fixing it here comes across as leaving the
camp slightly less in a bad shape than how I found it.

Co-authored-by: Simone Basso <bassosimone@gmail.com>

cmd/ooniprobe/internal/nettests/groups.go

@@ -37,6 +37,7 @@ var All = map[string]Group{
 			FacebookMessenger{},
 			Telegram{},
 			WhatsApp{},
+			Signal{},
 		},
 		UnattendedOK: true,
 	},
@@ -54,7 +55,6 @@ var All = map[string]Group{
 		Nettests: []Nettest{
 			DNSCheck{},
 			STUNReachability{},
-			Signal{},
 		},
 	},
 }