Remove automatic RPATH - adapt shlib_wrap.sh

Looking for something starting with '-Wl,-rpath,' isn't good enough,
as someone might give something like '-Wl,--enable-new-dtags,-rpath,/PATH'.
Looking for ',-rpath,' should be safe enough.

We could remove the preloading stuff entirely, but just in case the
user has chosen to given RPATH setting arguments at configuration,
we'd better make sure testing will still work.  Fair warning, there
are some configuration options that do not work with preloaded OpenSSL
libraries, such as the sanity checking ones.

Reviewed-by: Rich Salz <rsalz@openssl.org>