hg: jdk/submit12: 8216490: Spammy periodic GC log message contains random time stamp with periodic gc disabled

[thomas.schatzl at oracle.com]

Changeset: 528207d2e73e
Author:    tschatzl
Date:      2019-01-16 11:43 +0100
URL:       http://hg.openjdk.java.net/jdk/submit12/rev/528207d2e73e

8216490: Spammy periodic GC log message contains random time stamp with periodic gc disabled
Summary: Print periodic gc status at startup and only print regular messages if enabled.
Reviewed-by: sangheki, kbarrett

! src/hotspot/share/gc/g1/g1YoungRemSetSamplingThread.cpp
+ test/hotspot/jtreg/gc/g1/TestPeriodicLogMessages.java