[scudo] Relax the memalign test

Summary:
Now that we are not rounding up the sizes passed to the secondary allocator,
the memalign test could run out of aligned addresses to return for larger
alignments. We now reduce the size of the quarantine for that test, and
allocate less chunks for the larger alignments.

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27760

llvm-svn: 289665