innobackupex failed to copy-back backup if destination dir is not empty

Hi,

innobackupex requires empty destination dir in order to copy backup to it. I think this is wrong behaviour, because target dir could/should contain custom my.cnf or master.info files. In such a case innobackupex should not consider non empty dir as error.

How to reproduce:
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> ls -lh /var/192.168.1.7/mysql/
total 8,0K
-rw-rw---- 1 mysql mysql 69 Feb 18 23:08 master.info
-rw-r----- 1 mysql mysql 404 Feb 18 23:09 my.cnf
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> sudo innobackupex --copy-back /var/tmps/backup
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Original data directory is not empty! at /usr/bin/innobackupex line 574.
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Fix:
I have modified template which decides whether directory is empty or not.
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--if ( ! scalar( grep { $_ ne "." && $_ ne ".." } readdir($dh)) == 0) {
++if ( ! scalar( grep { $_ ne "." && $_ ne ".." && $_ ne "my.cnf" && $_ ne "master.info"} readdir($dh)) == 0) {
==