Avoid test failure due to broken dlpreloading of shared library.

Avoid test failure due to broken dlpreloading of shared library.

* tests/lt_dladvise.at (lt_dlopenadvise library loading): Drop
some newlines in AT_CHECK commands, for better 'testsuite -x'
output.  Only create a static installable libpreload.la, to
avoid exposing the bug libtool currently has with preloading of
shared libraries.  Add a note to revisit this later.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>