Fix to bug 567(http://bugs.mariadb.com/show_bug.cgi?id=567)
log_manager.cc: if the file exists, is a symbolic link and is not writable, the log manager does not fail but unlinks it and creates a new one.
Merge branch 'develop' into shm_log_fix
Merge branch 'develop' into shm_log_fix

Conflicts:
	log_manager/log_manager.cc
Merge branch 'shm_log_fix' into develop
Auth error message fix for using password: YES,NO

Auth error message fix for using password: YES,NO
This applies to a “not found user” trying to authenticate with or
without password
Merge branch 'develop' into MAX-309