Move from __future__ import to beginning of module

PEP 0236 [0] demands that "all future_statements must appear near the top of the
module." and that the only lines that can appear before a future_statment are
the module docstring, comments, blank lines or other future_statements

This commit fixes the following modules:

* salt.modules.macports
* salt.modules.mine
* salt.modules.mysql
* salt.modules.ps
* salt.modules.qemu_nbd
* salt.modules.selinux
* salt.modules.serverdensity_device
* salt.modules.state
* salt.modules.sysmod
* salt.modules.puppet

This commit fixes #17684

[0] http://legacy.python.org/dev/peps/pep-0236/