fixes reload Chan_dahdi memory leak caused by variables

chan_dahdi reloading with variables set via setvar in chan_dahdi.conf would
stay in the dahdi_pvt structs for individual channels (causing them to just
continue adding the new ones to the list) and also there was a memory leak
causes by the conf objects. This patch resolves both of these by using 
ast_variables_destroy during the loading process.

(closes issue #17450)
Reported by: nahuelgreco
Patches:
	patch.diff uploaded by jrose (license 1225)
	Tested by: tilghman, jrose

Review: https://reviewboard.asterisk.org/r/1170/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.2@313432 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_dahdi.c

@@ -10540,6 +10540,12 @@ static struct dahdi_pvt *mkintf(int channel, const struct dahdi_chan_conf *conf,
 	}
 
 	if (tmp) {
+		/* If there are variables in tmp before it is updated to match the new config, clear them */
+		if (reloading && tmp->vars) {
+			ast_variables_destroy(tmp->vars);
+			tmp->vars = NULL;
+		}
+
 		int chan_sig = conf->chan.sig;
 		if (!here) {
 			if ((channel != CHAN_PSEUDO) && !pri) {
@@ -18111,6 +18117,13 @@ static int process_dahdi(struct dahdi_chan_conf *confp, const char *cat, struct
 		} else if (!(options & PROC_DAHDI_OPT_NOWARN) )
 			ast_log(LOG_WARNING, "Ignoring any changes to '%s' (on reload) at line %d.\n", v->name, v->lineno);
 	}
+
+	/* Since confp has already filled invidual dahdi_pvt objects with channels at this point, clear the variables in confp's pvt. */
+	if (confp->chan.vars) {
+		ast_variables_destroy(confp->chan.vars);
+		confp->chan.vars = NULL;
+	}	
+
 	if (dahdichan[0]) {
 		/* The user has set 'dahdichan' */
 		/*< \todo pass proper line number instead of 0 */