cbcollect_info orders memcached.log.* files incorrectly

Shell orders file names in lexicographic order which does not always correspond to modification time for two reasons:

1. When restarted memcached will start counting files from the beginning (i.e. from memcached.log.0.txt)
2. Lexicographically memcached.log.10.txt is smaller than memcached.log.9.txt.

So modification time should be used explicitly.