loader: fix leak of child-to-parent links on dlclose()

Remove the code adding link from child to parent. The link is
not used anywhere in the linker for L release.

Bug: 36104177
Test: manual - dlopen/dlclose libandroid.so 10 times and see how many blocks are
      used after each dlclose() - make sure they are constant.

Change-Id: I57039e934ba233253ad7dce2e071833528460116