slaprunner: try opening locked tables for 5 seconds in case database is locked by another process

On runner importer script, when updating database, set timeout to 5 seconds (same value as the default in python sqlite3 module: https://docs.python.org/2.7/library/sqlite3.html#sqlite3.connect). If database is locked by another process we wait a bit instead of raise immediately "database is locked". Importer script will raise if database is locked for more than 5 seconds.