I've seen the same thing on a system running stretch, there is no encryption. It is an LVM setup with root and var in logical volumes.
Very early in the boot, after about 6 or 7 other lines appear in the console, I see WARNING: Failed to connect to lvmetad. Falling back to internal scanning. Reading the lvmetad man page, it suggested that it may be necessary to run 'pvscan --cache' to initialize the cache. I tried that and then rebooted, the same warning still appears.
