Corrected spelling error

Fixes error event with message: 'MySqlDeadlockPlugin' object has no attribute 'deadlock_time'
Merge branch 'develop' of https://github.com/zenoss/ZenPacks.zenoss.MySqlMonitor into develop
ZEN-10314: use severity specified on the datasource for connection error events
Fixed tests
Merge pull request #23 from ssirushchyshyn/develop

ZEN-10314