Move rate_ctr free to tbf subclass destructor

This way we clean up tbf_free entry point, and leave memory freeing for
later on at the end when talloc_free is called.

Change-Id: I1c45e3296e565725bcbbca391d9518772fffa89d
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index e76ea8c..0330a78 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -180,7 +180,12 @@
 gprs_rlcmac_dl_tbf::~gprs_rlcmac_dl_tbf()
 {
 	osmo_timer_del(&m_llc_timer);
-	/* ~gprs_rlcmac_dl_tbf() is called automatically upon return */
+	if (is_egprs_enabled()) {
+		rate_ctr_group_free(m_dl_egprs_ctrs);
+	} else {
+		rate_ctr_group_free(m_dl_gprs_ctrs);
+	}
+	/* ~gprs_rlcmac_tbf() is called automatically upon return */
 }
 
 gprs_rlcmac_dl_tbf::gprs_rlcmac_dl_tbf(struct gprs_rlcmac_bts *bts_, GprsMs *ms) :