RFR: Still need to call make_tlabs_parsable() even UseTLAB is disabled

[Zhengyu Gu]

We missed make_tlabs_parsable() call when preparing for full gc when 
UseTLAB is disabled, we still need it to retire PLAB.

http://cr.openjdk.java.net/~zgu/shenandoah/fullgc_retire_plab/webrev.00/

We should consider to breakup it into two? cause it is confusing to call 
it when UseTLAB is off.


Test:

   tier2_gc_shenandoah


Thanks,

-Zhengyu