master: Add AUTO_RECOVERY option

This commit introduces a possibility to apply changelogs in the master
server's process. This feature makes it possible to start master server
without using mfsmetarestore after a crash, ie. when changes from
changelog.0.mfs need to be applied to the metadata.mfs file. When there
is a AUTO_RECOVERY = 1 option in the master server's configuration file
set, it will automatically perform this task before starting if it's
needed (ie. if there is a stale metadata.mfs.lock file left). If
AUTO_RECOVERY = 0, it will refuse to start in such a case.

Change-Id: Ib9509c5dba130c52c3c7d15605a41c74a865e3d0
tests: Add tests for applying changelogs by the master server

Added tests for automatic recovery in case of the master server crash,
ie. reading metadata information from changelog while starting,
performing full lizardfs build while killing the master server.

Change-Id: I4080e46724d93830c014e1f276359cb06f05f944