none/tests/amd64-linux/map_32bits.vgtest fails too easily

none/tests/amd64-linux/map_32bits.vgtest fails too easily

On various systems none/tests/amd64-linux/map_32bits.vgtest fails with:
first mmap: Cannot allocate memory.

The problem is that the --aspace-minaddr is too tight. Newer glibc seem
to mmap some memory and so even our first mmap with MMAP_32BIT will fail.

The solution is to make a bit more memory < 2GB available.
If there is 16MB available the test always seems to succeed without
needing too many tries. The original 256K is too low.

https://bugs.kde.org/show_bug.cgi?id=406422