Small change to test_exe to point to /usr/bin/python

- Simple fix to make all unittests green

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Fix imports in correct files

sos/archive.py:
    - Archive uses selinux module but wasn't included
sos/policies/__init__:
    - sys.exit called without sys import

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
pyflakes results

sos/plugins/cgroups.py:
    - Fix call to non existent cgroups method
sos/plugins/{dhcp,iscitarget}.py:
    - Fix class call names
sos/plugins/process.py:
    - Remove random method calling nonexistent routines
sos/plugins/selinux.py:
    - Fix call to do_regex_findall

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Merge pull request #128 from battlemidget/pyflakes-fixes

Pyflakes fixes