Restore case-insensitive de-duplication of statuses

A refactoring of FillCache, 6eac780, removed the lc() from two de-duping
statements, presumably in a premonition about the following commit,
15857be, which forced statuses to lowercase.

However, the next commit to follow that, 3af6cb0, introduced
case-preservation for statuses while still keeping case-insensitivity.
It neglected to add back the lc()s to the de-duping which became
necessary once statuses could again vary in displayed case.
Compare the special "deleted" status case insensitively

Statuses returned by RT::Lifecycle or RT::Ticket->Status are in
canonical case rather than guaranteed lower case.  When comparing
statuses, both operands should be lowercased.
Merge branch '4.0/lifecycle-case-comparisons' into 4.0-trunk