efi_selftest: add tests for QueryVariableInfo at boottime

Previous patches added QueryVariableInfo at runtime tests and
split a common function that can be used at boottime. Weire it
up and run a similar set of tets. While at it move a test which is
checiking for 0 available storage in the common code

Add tests for
- Test QueryVariableInfo returns EFI_SUCCESS
- Test null pointers for the function arguments
- Test invalid combination of attributes

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>