res_pjsip_endpoint_identifier_ip: Add 'show identify(ies)' cli commands

While troubleshooting other things I realized there were no pjsip cli
commands for identify.  This patch adds them.  It also also fixes a
reference leak when a 'show endpoint' displayed identifies and properly
sets the return code if load_module can't allocate a cli formatter structure.

Tested-by: George Joseph

Review: https://reviewboard.asterisk.org/r/4212/
........

Merged revisions 428725 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/13@428731 f38db490-d61c-443f-a65b-d21fe96a405b
config: Create ast_variable_find_in_list()

Add
const char *ast_variable_find_in_list(const struct ast_variable *list,
   const char *variable);

ast_variable_find() requires a config category to search whereas
ast_variable_find_in_list() just needs the root list element which is
useful if you don't have a category.

Tested-by: George Joseph

Review: https://reviewboard.asterisk.org/r/4217/
........

Merged revisions 428733 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/13@428734 f38db490-d61c-443f-a65b-d21fe96a405b