revert movement of unit alignment init to initializer list

*** Please don't merge! This appears to break something. ***

This change was suggested by gfgtdf, it partially reverts

https://github.com/wesnoth/wesnoth/commit/30c179b92da29bb03541e8e0c7dfaf1c3c401b35#diff-af3fd7e884f8ab9f39f9088ca4010d0dR1738

It fails unit tests on my machine and so I don't think it should
be committed.