add simple corosync config parser self check

add simple corosync config parser self check

Each test reads and parses a config "writes" it again and then
re-parses it.
Then both the parsed hash structures and the raw config get compared
This is cheap and should catch simple regressions in either the
parser or writer, as currently we have no safety net that
modifications on either one didn't cause regressions.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>