Fix UnnecessaryParentReference handling of concatenated `&`

Fix issue where the linter would report an incorrect lint for code like
the following:

    & + &:hover {
      ...
    }

Change-Id: Iac35b0e68265f5c029b8d28f0685bba24c1d0df8
Reviewed-on: http://gerrit.causes.com/43355
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>