Revert "linker: disable ld.config.txt in ASAN mode"

This reverts commit 81b17574.

Reason: 02586a2a fixed the bug that
prevented us from using LD_PRELOAD with multiple namespaces.

Bug: 38114603
Test: 1. ./external/compiler-rt/lib/asan/scripts/asan_device_setup --lib
prebuilts/clang/host/linux-x86/clang-stable/lib64/clang/5.0/lib/linux
2. enable talkback shortcut
3. in the home screen, hold vol-up/down together
4. device does not reboots and talkback shortcut is toggled
Test: bionic-unit-tests and linker-unit-tests successful

Merged-In: I25a05927ffbb28b9fa72303652893f43918ccec6
Change-Id: Ib7568d65c2524fd2307d01eb3d50fc308feced9c
(cherry picked from commit 6ab40bbf)