bts: fix uninitialized memaccess in BTS::send_gsmtap_rach()

Unfortunately, RACH.ind on the PCU interface contains no Uplink
measurements: neiter RSSI nor C/I.  In order to avoid sending
garbage, let's zero-initialize 'struct pcu_l1_meas'.

Change-Id: I8c3210c428da17d23d798f3ef9df941ded6e162a
Fixes: CID#216512
diff --git a/src/bts.cpp b/src/bts.cpp
index bd0a1d2..87afc9f 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -506,7 +506,7 @@
 void BTS::send_gsmtap_rach(enum pcu_gsmtap_category categ, uint8_t channel,
 			   const struct rach_ind_params *rip)
 {
-	struct pcu_l1_meas meas;
+	struct pcu_l1_meas meas = { 0 };
 	uint8_t ra_buf[2];
 
 	/* 3GPP TS 44.004 defines 11 bit RA as follows: xxxx xxxx  .... .yyy