RFR: 8148755: -XX:+HeapDumpAfterFullGC creates heap dump both before and after Full GC

[Claes Redestad]

Hello,

this patch fixes an issue where heap is dumped both before and after 
full GC if either one of -XX:+HeapDumpAfterFullGC or 
-XX:+HeapDumpBeforeFullGC is specified.

Bug: https://bugs.openjdk.java.net/browse/JDK-8148755
Webrev: http://cr.openjdk.java.net/~redestad/8148755/webrev.01

Testing: JPRT, manual verification

Thanks!

/Claes