Build fixes

* Don't execute PEP8 checks when PEP8 is not installed
* configure.ac: Don't fail on systems where AM_PROG_AR is not yet
  available in automake
* m4/fhs.m4 don't fail if neither /var/lock/subsys nor /var/lock
  are present

Change-Id: Iaa33a029b2e8fbbbd2e1329814dd8dc182109552
Signed-off-by: Vinzenz Feenstra <vfeenstr@redhat.com>