Camera3Device: Fix regression to old camera API operation.

When Camera2Client uses Camera3Device, it operates with lazy stream
configuration (in which streams are configured only once a capture
request is going to actually be sent). In this path, the operating
mode may never get set to a valid mode, and thus always fail
stream configuration.

Ensure that all paths calling into configureStreamsLocked set the
appropriate operating mode.

Test: Actually no camera CTS regressions this time, honest!
Bug: 34853980
Change-Id: I6e1855206f6d76cca5ff8348555b26bd7b868843