gbproxy/test: Don't assign a variable within OSMO_ASSERT (Coverity)

Coverity complains about having side effects in OSMO_ASSERT argument
expressions. This would be an issue in this case, because that
variable is only reference in other OSMO_ASSERT expressions.

Nevertheless this patch changes this to assign the variable outside
of OSMO_ASSERT.

Fixes: Coverity CID 1244239
Sponsored-by: On-Waves ehf
diff --git a/openbsc/tests/gbproxy/gbproxy_test.c b/openbsc/tests/gbproxy/gbproxy_test.c
index 5aa301b..16dbf5b 100644
--- a/openbsc/tests/gbproxy/gbproxy_test.c
+++ b/openbsc/tests/gbproxy/gbproxy_test.c
@@ -1557,7 +1557,7 @@
 	struct gbproxy_link_info *link_info;
 	struct gbproxy_peer *peer;
 	LLIST_HEAD(rcv_list);
-	struct expect_result *er;
+	struct expect_result *expect_res;
 
 	OSMO_ASSERT(local_tlli == gprs_tmsi2tlli(ptmsi, TLLI_LOCAL));
 
@@ -1742,8 +1742,9 @@
 		       GPRS_SAPI_GMM, 3,
 		       dtap_act_pdp_ctx_req, sizeof(dtap_act_pdp_ctx_req));
 
-	OSMO_ASSERT(er = expect_gmm_msg(SGSN_NSEI, 0x1002, GSM48_MT_GSM_ACT_PDP_REQ));
-	OSMO_ASSERT(er->parse_ctx.apn_ie_len == gbcfg.core_apn_size + 2);
+	expect_res = expect_gmm_msg(SGSN_NSEI, 0x1002, GSM48_MT_GSM_ACT_PDP_REQ);
+	OSMO_ASSERT(expect_res != NULL);
+	OSMO_ASSERT(expect_res->parse_ctx.apn_ie_len == gbcfg.core_apn_size + 2);
 
 	OSMO_ASSERT(8 == peer->ctrg->ctr[GBPROX_PEER_CTR_RAID_PATCHED_BSS].current);
 
@@ -1756,8 +1757,9 @@
 		       GPRS_SAPI_GMM, 3,
 		       dtap_act_pdp_ctx_req, sizeof(dtap_act_pdp_ctx_req));
 
-	OSMO_ASSERT(er = expect_gmm_msg(SGSN_NSEI, 0x1002, GSM48_MT_GSM_ACT_PDP_REQ));
-	OSMO_ASSERT(er->parse_ctx.apn_ie_len == 0);
+	expect_res = expect_gmm_msg(SGSN_NSEI, 0x1002, GSM48_MT_GSM_ACT_PDP_REQ);
+	OSMO_ASSERT(expect_res != NULL);
+	OSMO_ASSERT(expect_res->parse_ctx.apn_ie_len == 0);
 
 	OSMO_ASSERT(9 == peer->ctrg->ctr[GBPROX_PEER_CTR_RAID_PATCHED_BSS].current);
 
@@ -1809,8 +1811,9 @@
 		       GPRS_SAPI_GMM, 3,
 		       dtap_act_pdp_ctx_req, sizeof(dtap_act_pdp_ctx_req));
 
-	OSMO_ASSERT(er = expect_gmm_msg(SGSN_NSEI, 0x1002, GSM48_MT_GSM_ACT_PDP_REQ));
-	OSMO_ASSERT(er->parse_ctx.apn_ie_len == 0);
+	expect_res = expect_gmm_msg(SGSN_NSEI, 0x1002, GSM48_MT_GSM_ACT_PDP_REQ);
+	OSMO_ASSERT(expect_res != NULL);
+	OSMO_ASSERT(expect_res->parse_ctx.apn_ie_len == 0);
 
 	OSMO_ASSERT(13 == peer->ctrg->ctr[GBPROX_PEER_CTR_RAID_PATCHED_BSS].current);