RFR(XS): [8u] Fixed message logging

[Aleksey Shipilev]

On 08/23/2017 02:32 PM, Zhengyu Gu wrote:
> GC logging with sub-tags are filtered out, such as gc+ergo, gc+init and etc.
> 
> Webrev: http://cr.openjdk.java.net/~zgu/shenandoah/8u_logging/webrev.00/

Does that mean (gc,ergo) messages are always printed now? I think -verbose:gc should enable (gc)
only to have a brief GC log, and -XX:+PrintGCDetails should enable (gc, *), which should print
everything else too.

Please also fix two related TODOs, grep for:

  // TODO: This should really be (gc,ergo)

Thanks,
-Aleksey