Clean up multipath linking

Clean up multipath linking

This is a patch to fix up the linking. It does two things.  First, it makes
libmultipath.so install to /lib/ just like a normal shared library, so you
don't have to use -rpath to link to it.  Second, and more importantly,
it moves the libaio linking into libcheckdirectio.so, where it belongs.  Since
libcheckdirectio.so is a dynamic shared object, multipath and multipathd don't
know what functions they need to link in from libaio. This fixes the directio
lockup for me.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>