lib/event/app: Remove use of perror() for malloc() failure

All SPDK libraries should use the spdk/log.h family of functions
for logging.

Change-Id: I4b9f172102c6d7998d3a634573493db3fe25ff76
Signed-off-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-on: https://review.gerrithub.io/391686
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>

lib/event/app.c

@@ -143,7 +143,7 @@ spdk_app_get_running_config(char **config_str, char *name)
 
 	*config_str = malloc(length + 1);
 	if (!*config_str) {
-		perror("config_str");
+		SPDK_ERRLOG("out-of-memory for config\n");
 		fclose(fp);
 		return -1;
 	}