Fix asan path translation loading a library twice.

An ASan binary may load a non-ASan library from /system if /data is not mounted yet.
A dlopen() call for the same library later, when /data/ is available, will translate the path and attempt to load
an ASan copy of the library from /data/asan/system. This way we may end up loading both ASan and non-ASan copies of
the library in the same process, which is a very bad thing.

This change adds a check for a loaded library with the non-translated real path before applying path translation.

Bug: 63622872
Test: hide/rename a library in /data/asan; dlopen; restore the library; dlopen; check that the library from /data/asan is NOT loaded.
Change-Id: I17060837f08dc3c665cab803dd89979d88f0a019