Change ngx_rtmp_exec_run return type to void

[StepanGulyaev]

The Svace SAST tool have found an issue in using of ngx_rtmp_exec_run function. The function has ngx_int_t return value type but this value is never checked throughout the code. For example:

nginx-rtmp-module/ngx_rtmp_exec_module.c

Line 638 in 6c7719d

ngx_rtmp_exec_run(e);

nginx-rtmp-module/ngx_rtmp_exec_module.c

Lines 610 to 615 in 6c7719d

	#if !(NGX_WIN32)
	static void
	ngx_rtmp_exec_respawn(ngx_event_t *ev)
	{
	ngx_rtmp_exec_run((ngx_rtmp_exec_t *) ev->data);
	}

nginx-rtmp-module/ngx_rtmp_exec_module.c

Line 1134 in 6c7719d

ngx_rtmp_exec_run(&en);

nginx-rtmp-module/ngx_rtmp_exec_module.c

Lines 1154 to 1156 in 6c7719d

	if (ngx_rtmp_exec_filter(s, en->conf) == NGX_OK) {
	ngx_rtmp_exec_run(en);
	}

All functions that call ngx_rtmp_exec_run are also static void functions so they can't send that value further up and it it's not convinient thing to do.

ngx_rtmp_exec_run prints all required debug data to logs and we won't lose anything if we remove return NGX_ERROR or NGX_OK values and SAST tools will stop triggering on those.