Fix potential crash when entire span request is received.

The variable index used in this scenario for accessing the dahdi_pvts was
wrong and was most likely copied from the several other places it is used
correctly.

(closes issue #15998)
Reported by: tsearle
Patches: 
      dahdi_reset_crash.patch uploaded by tsearle (license 373)


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@222393 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_dahdi.c

@@ -9180,8 +9180,8 @@ static void *pri_dchannel(void *vpri)
 								pri_destroycall(pri->pri, pri->pvts[x]->call);
 								pri->pvts[x]->call = NULL;
 							}
-							if (pri->pvts[chanpos]->realcall) 
-								pri_hangup_all(pri->pvts[chanpos]->realcall, pri);
+							if (pri->pvts[x]->realcall) 
+								pri_hangup_all(pri->pvts[x]->realcall, pri);
  							else if (pri->pvts[x]->owner)
 								pri->pvts[x]->owner->_softhangup |= AST_SOFTHANGUP_DEV;
 							ast_mutex_unlock(&pri->pvts[x]->lock);