main/format_cap: Parse capabilities generated by ast_format_cap_get_names

We have a strange relationship between the parsing of format
capabilities from a string and their representation as a string. We
expect the format capabilities to be expressed as a string in the
following format:

allow = !all,ulaw,alaw
disallow = g722

While we would generate the string representation of those formats as:

allow = (ulaw|alaw)
disallow = (ulaw|alaw|g729...)

When the configuration framework needs to store values as a string, it
generates the format capabilities using the second representation; this
representation however cannot be parsed when the entry is rehydrated.
This patch fixes that by updating
ast_format_cap_update_by_allow_disallow to parse an entry as if it were
in the generated format if it has a leading '(' and a trailing ')'.

ASTERISK-25238

Change-Id: I904d43caf4cf45af06f6aee0c9e58556eb91d6ca

main/format_cap.c

@@ -293,7 +293,24 @@ int ast_format_cap_update_by_allow_disallow(struct ast_format_cap *cap, const ch
 	}
 
 	parse = ast_strdupa(list);
-	while ((this = strsep(&parse, ","))) {
+
+	/* If the list is being fed to us as a result of ast_format_cap_get_names,
+	 * strip off the paranthesis and immediately apply the inverse of the
+	 * allowing option
+	 */
+	if (parse[0] == '(' && parse[strlen(parse) - 1] == ')') {
+		parse++;
+		parse[strlen(parse) - 1] = '\0';
+
+		if (allowing) {
+			ast_format_cap_remove_by_type(cap, AST_MEDIA_TYPE_UNKNOWN);
+		} else {
+			ast_format_cap_append_by_type(cap, AST_MEDIA_TYPE_UNKNOWN);
+		}
+	}
+
+
+	while ((this = strsep(&parse, ",|"))) {
 		int framems = 0;
 		struct ast_format *format = NULL;