Reduce the size of quarantine cache in ASAN_LOW_MEMORY configuration.

Summary:
Experiments show that on Android the current values result in too much
of the memory consumption for all quarantined chunks.

Reviewers: kcc, eugenis

Subscribers: mgorny, danalbert, srhines, llvm-commits, kubabrecka

Patch by Aleksey Shlyapnikov.

Differential Revision: https://reviews.llvm.org/D27873

llvm-svn: 290218