build-tests: The allowed method is used by default

The allowed method returns true when the feature is set to `enabled`
or `auto`.

The allowed method returns false when the feature is set to
`disabled`.

So we prefer to use the `allowed` method instead of `enabled`.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: If19f03ed8a9e15009d97009101135d36573773ac
1 file changed