#61 Decompression of wals during recover depend only of conf file, not wals compression

[Alain Radix]

I create backups without wal compression in barman.conf, then change for compression in barman.conf and recover.
This give me this error :
Copying required wal segments.
EXCEPTION: {'err': u'bzip2: (stdin) is not a bzip2 file.\n', 'ret': 2, 'out': u''}
See log file for more details.

While the compression used to store the wal is registered in xlog.db and that the file compression can be know using the unix utility file, the choice to use a decompression utility for recover is only done from the configuration of the file barman.conf.
This is obviously not a good idea as changing the configuration invalidate previously store wals without real reason.

[Gabriele Bartolini]

Fixed with [5a1384b4da9c92bf73b0ebcff207c10728369bfd]