lsd-admin: error message if .__dblock.lock already present in $LSD_DB

[willclarkson]

Would it be possible for lsd-admin to warn the user and exit gracefully if the .__dblock.lock file is present in $LSD_DB? Currently the software just seems to hang on encountering this file.

lsd-admin already gracefully exits if the .__transaction file is present, alerting the user; the same behavior would be useful on encountering the .__dblock.lock file.