Use more reasonable cause code when rejecting incoming call waiting calls.

(closes issue ASTERISK-19397)
Reported by: Birger Harzenetter
Patches:
      nochannel-cause.patch (license #5870) patch uploaded by Birger Harzenetter
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Merged revisions 357407 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 357408 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@357409 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/sig_pri.c

@@ -5909,7 +5909,7 @@ static void *pri_dchannel(void *vpri)
 #endif	/* defined(HAVE_PRI_CALL_WAITING) */
 					{
 						/* We will not accept incoming call waiting calls. */
-						pri_hangup(pri->pri, e->ring.call, PRI_CAUSE_INCOMPATIBLE_DESTINATION);
+						pri_hangup(pri->pri, e->ring.call, PRI_CAUSE_NORMAL_CIRCUIT_CONGESTION);
 						break;
 					}
 #if defined(HAVE_PRI_CALL_WAITING)