RFR (XS): 8233597: Clean up code in G1Analytics::compute_pause_time_ratio

[Thomas Schatzl]

Hi all,

   can I have reviews for this change that cleans up some code 
equivalent to the clamp() method introduced in JDK-8233702?

CR:
https://bugs.openjdk.java.net/browse/JDK-8233597
Webrev:
http://cr.openjdk.java.net/~tschatzl/8233597/webrev/
Testing:
hs-tier1-5 with other patches

Thanks,
   Thomas