Look into ld_preloads before current library

 Change lookup order during relocation so that
 ld_preloads always precede caller (unless caller
 is main executable).

 Asan needs this change in order to intercept libc->libc
 calls.

Bug: 15432753
(cherry picked from commit 05e190c0)

Change-Id: I5bfb58e18015b1ec5b77842dbb37fb122fa1fd1a