gbproxy: Reduce timeout to fix flaky test

The individual timeouts in TC_BVC_bringup_conflicting add up to almost
15.0s (the Tguard timeout) which causes the test to sometimes fail.
Decrease the time waiting for all BVCs to be unblocked from 10s to 5s,
in reality this should be plenty time.

Change-Id: I620ce90f9e6b54cc94b4d36ac123f43d8d809f47
diff --git a/gbproxy/GBProxy_Tests.ttcn b/gbproxy/GBProxy_Tests.ttcn
index ac81580..e5bec7d 100644
--- a/gbproxy/GBProxy_Tests.ttcn
+++ b/gbproxy/GBProxy_Tests.ttcn
@@ -1114,7 +1114,7 @@
 	}
 
 	/* wait until all BVC are unblocked on both sides */
-	timer T := 10.0;
+	timer T := 5.0;
 	T.start;
 	alt {
 	[] SGSN_MGMT.receive(BssgpStatusIndication:{*, ?, ?}) {