res_statsd: Fix exports.in for missing symbols

res_statsd.export.in was missing the _va variations of the log
functions causing Asterisk to crash in res_pjsip if OPTIONAL_API
wasn't enabled.

ASTERISK-25727 #close
Reported-by: Gergely Dömsödi

Change-Id: I395729f9f51bdd33c5ca757f5f96ebedad74077b

res/res_statsd.exports.in

 {
 	global:
-		LINKER_SYMBOL_PREFIX*ast_statsd_log;
-		LINKER_SYMBOL_PREFIX*ast_statsd_log_full;
-		LINKER_SYMBOL_PREFIX*ast_statsd_log_sample;
-		LINKER_SYMBOL_PREFIX*ast_statsd_log_string;
+		LINKER_SYMBOL_PREFIXast_statsd_log*;
 	local:
 		*;
 };