- markvoldirty() needs to write to underlying GEOM provider. We
have to do that *before* g_access() which sets the GEOM provider
to read-only.
- Remove dirty flag before free'ing iconv related resources. The
dirty flag removal could fail, and it is hard to revert the
iconv-free after the fail.
- Mark volume as dirty if we have failed to mark it clean for safe.
- Other style fixes to the touched functions.