Remove old flagfile support.
Remove old flagfile support.

Implements blueprint remove-old-flagfile

nova-manage can still be used to convert old flagfiles style files
to new .ini files:

$ ./bin/nova-manage  config  convert --help
Usage: nova-manage config convert <args> [options]

Options:
  -h, --help        show this help message and exit
  --infile=<path>   old-style flagfile to convert to config
  --outfile=<path>  path for output file. Writes configto stdout if not
                    specified.

Change-Id: Ib8fbbd858b1db7faef70d7d97955e5042bf378f2
Signed-off-by: Ghe Rivero <2e4790562711923f45b41a0580b92090cd94a2e1@debian.org>

openstack/oslo.versionedobjects,citrix-openstack-build/oslo.versionedobjects