staging: lustre: selftest: fix "not declared" by declaring in header

Fix several "symbol '...' was not declared" sparse warnings which
are caused by global variables by declaring them in the header file.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>