[cleanup] Fix warnings in gridadapt.

- Wrong order of initializing member variables.
- Remove unused variable.
No warning:
- Remove semicolon after methods.
- Drop continue, use negated if statement.
(reviewed by martins)


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@14646 2fb0f335-1f38-0410-981e-8018bf24f1b0