fix gsm0808_enc_cell_id_list2 for leading-zero MNC

Use non-deprecated API to decode encode in gsm0808_enc_cell_id_list2().

Adjust gsm0808_test.c to now expect the correct results instead of previous
failure.

Change-Id: I1ce78883995e0d484368046b69db5afb2b4adc97
diff --git a/tests/gsm0808/gsm0808_test.c b/tests/gsm0808/gsm0808_test.c
index f6a7bc4..4bf61e7 100644
--- a/tests/gsm0808/gsm0808_test.c
+++ b/tests/gsm0808/gsm0808_test.c
@@ -1003,8 +1003,7 @@
 	uint8_t cil_enc_expected[] = { GSM0808_IE_CELL_IDENTIFIER_LIST, 0x16, 0x00,
 		0x21,  0x63,  0x54,  0x23,  0x42,  0x00,  0x1,
 		0x21,  0xf4,  0x75,  0x24,  0x43,  0x00,  0x2,
-		0x21,  0xf5,  0x70,  0x25,  0x44,  0x00,  0x77
-	/*   ERROR! This ^^^^^^^^ should be 0x75, 0x00, i.e. a 3-digit MNC with leading zeros! */
+		0x21,  0x75,  0x00,  0x25,  0x44,  0x00,  0x77
 	};
 	uint8_t rc_enc;
 	int rc_dec, i;
@@ -1057,9 +1056,7 @@
 		struct osmo_cell_global_id *dec_id;
 		enc_id = &enc_cil.id_list[i].global;
 		dec_id = &dec_cil.id_list[i].global;
-		/* ERROR: the decoded PLMN will mismatch, because the leading zero was not preserved:
 		OSMO_ASSERT(osmo_plmn_cmp(&enc_id->lai.plmn, &dec_id->lai.plmn) == 0);
-		*/
 		OSMO_ASSERT(enc_id->lai.lac == dec_id->lai.lac);
 		OSMO_ASSERT(enc_id->cell_identity == dec_id->cell_identity);
 	}