Fix missing zone strings in some cases

ICU's TimeZoneNames requires a "canonical" zone ID, otherwise it will
return no data. Usually the ID being used is the same as the canonical
ID so there's no problem. This change is based on an equivalent fix in
the newer SettingsUI code. It is for completeness, to ensure incorrect
code is not copied in future.

Bug: 155167041
Test: None
Change-Id: I2becbebb0213c4aa60031178a760ee12bfb7d295