Fix org#2567 Device don't always get the right "capabilities"

Fix org#2567 Device don't always get the right "capabilities"

- "capabilities" was sometime adjusted in the constructor or in the factory
  function, but device_generic_init() that is called later by init_dev()
  initialize most of the device fields including "capabilities"
- move the tweak of the "capabilities" in device_specific_init()
  that is called after device_generic_init()
- update the device_generic_init() method of all concerned classes
- doing only a return file_dev::device_specific_init(); in child class is
  useless (not overwriting the method would be ok) but I want to be
  sure that nobody will forget to do it if device_specific_init() is
  modified
- testing can be done by searching for "Ready to append to end of Volume"
  in job log of "tests/restart-job-test"