Fix -Wundef warnings in login/tst-utmp.c.

Fix -Wundef warnings in login/tst-utmp.c.

To remove -Wno-error=undef, we need to fix the remaining cases where
there are -Wundef warnings in the testsuite.  One of those places is
in login/tst-utmp.c.

When included from tst-utmpx.c, <utmpx.h> is included instead of
<utmp.h>, meaning the _HAVE_UT_* macros are not defined.  The test is
prepared for them not being defined, in that all the relevant
conditionals also include "defined UTMPX".  However, they test the
_HAVE_UT_* macros first, so resulting in -Wundef warnings.

This patch does the minimal fix of swapping the || operands.  This is
logically correct - avoiding checking a macro we know will not be
defined in the case where it is not defined.  It won't fix such
warnings for the case where the toplevel bits/utmp.h is used and most
_HAVE_UT_* aren't defined at all even when <utmp.h> is included, but
that case doesn't apply to any current glibc configuration.  Fixing it
would also be tricky in that, while glibc itself consistently uses
_HAVE_UT_* in ways that would work with 0 instead of undefined,
external packages that use the macros expect defined / undefined
instead of 1 / 0 (codesearch.debian.net shows uses by util-linux,
python-utmp, libsys-utmp-perl).

Tested for x86_64.

	* login/tst-utmp.c [_HAVE_UT_TYPE || defined UTMPX]: Change
	conditional to [defined UTMPX || _HAVE_UT_TYPE].
	[_HAVE_UT_TV || defined UTMPX]: Change conditional to [defined
	UTMPX || _HAVE_UT_TV].
	[_HAVE_UT_TV - 0 || defined UTMPX]: Change conditional to [defined
	UTMPX || _HAVE_UT_TV - 0].