Use libcutils_headers for android_filesystem_config.h

android_filesystem_config.h is found since system/core/include is on
the include path for all projects and contains a symlink to the real
android_filesystem_config.h.  This is fragile and the below bug seeks
to remove this symlink and have users correctly depend on
libcutils_headers.

Bug: 165825252
Test: build
Change-Id: I244149c2eaf9beefbb8f0e1a0f20cf1adec684eb