BTS_Tests: default value for mp_ipa_up_timeout too low

The default value for the module parameter mp_ipa_up_timeout is set to
10 sec. Given that the sysmobts needs around 10-11 sec. to perform one
restart cycle this is to low and causes tests to fail occasionally. Lets
increase the default value to 15 sec to get reliable.

Change-Id: I5bb290d00a02a25672305688352a03f3bf484ff3
Related: OS#3863
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 711947a..68c85fb 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -64,7 +64,7 @@
 	integer mp_ms_actual_ta_exp := 0;
 	integer mp_timing_offset_256syms_exp := 512;
 	/* Time to wait for RSL conn from BTS during startup of test */
-	float mp_ipa_up_timeout := 10.0;
+	float mp_ipa_up_timeout := 15.0;
 }
 
 type record of RslChannelNr ChannelNrs;