qemu: Clean up virQEMUCapsFindBinaryForArch()
qemu: Clean up virQEMUCapsFindBinaryForArch()

If we get to the bottom of the function we know that none of the
attempts to locate a QEMU binary has been successful, so we can
simply return NULL directly.

This makes it unnecessary variable used to store the path, for
which we can use a more descriptive name.

Lastly, comparing with NULL explicitly is somewhat uncommon in
libvirt and more verbose than the equivalent implicit comparison,
so get rid of it.

Signed-off-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>
Reviewed-by: Daniel P. Berrangé <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>
Tested-by: Jim Fehlig <39929b5b86d72d51fceac59b52303e3fe8a3083e@suse.com>

olafhering/libvirt,olafhering/libvirt,crobinso/libvirt,jfehlig/libvirt,zippy2/libvirt,jfehlig/libvirt,crobinso/libvirt,crobinso/libvirt,jfehlig/libvirt,libvirt/libvirt,zippy2/libvirt,libvirt/libvirt,zippy2/libvirt,olafhering/libvirt,olafhering/libvirt,libvirt/libvirt,libvirt/libvirt,jfehlig/libvirt,zippy2/libvirt,crobinso/libvirt