RFR (XXS): 8037951: Remove "Code Root Fixup" in logs

[Thomas Schatzl]

Hi all,

  please review this small change removing obsolete code. In particular,
we still measured a "Code Root Fixup" phase which does not contain any
code to measure (okay, it actually did measure the destructor of the
StrongRootsScope, but this was not intentional I guess :)).

This change removes this phase from the logs and all related code.

Webrev:
http://cr.openjdk.java.net/~tschatzl/8037951/webrev/

CR:
https://bugs.openjdk.java.net/browse/JDK-8037951

Testing:
Jprt, jtreg in GC directory

Thanks,
  Thomas