Fix to actually load the real libGL.so when the application asks for it.
Our wrapper library intercepts calls to dlopen "libGL.so" and returns
a handle to itself. That's correct, and as intended.
Before doing this, however, it's essential to actual dlopen "libGL.so"
for real even though we won't be returning a handle to it. This
ensures that any side effects from that dlopen are taken care of.
This fixes a bug where "fips apitrace replay foo.trace" would cause
Mesa to fail to load its driver as follows (with LIBGL_DEBUG=verbose):