Speed up test 080-oom-throw

Reduce heap size, optimize blowup. The test just checks that OOME
get thrown for a fe basic operations. This is the same on all heap
sizes, just slower for larger heaps.

Before:
real  1m13.247s
user  1m11.115s
sys 0m1.834s

After:
real  0m26.604s
user  0m25.470s
sys 0m0.696s

Bug: 36501991
Test: time test/run-test --host 080-oom-throw

Change-Id: Id9d1ba702949a1f6070f6f20fb457e1749f90f25