pkg/host: refactor machine info tests
pkg/host: refactor machine info tests

Refactor tests so that they can be used with canned info.
The test fails for lots of different archs and we don't have any tests,
so these will keep breaking.
This change prepared for tests with canned info.

google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller