Commit d9f19c30 moved a lot of the
configuration setup into libxlDriverConfigNew().
However that tries to create the libxl/libxl-driver.log before the
libxl directory gets created in libxlStateInitialize().

This causes the daemon to fail on systems that have not had the directory
created before.

Move the code to create the libxl directory into libxlDriverConfigNew().
Signed-off-by: NStefan Bader <stefan.bader@canonical.com>