dlopen() has no NO_LOAD option before Android L.

This change could result in multiple instances of the shared library being
loaded when using alternate paths. This will be addressed by b/18752589.

Change-Id: Icf26a0c6f76edfd4f1c710e14f1005138d97e77a
Reviewed-on: https://swiftshader-review.googlesource.com/2664
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Greg Hartman <ghartman@google.com>