Don't munge timestamp in structured logs, again

Structured logging tools expect a POSIX timestamp.
0a887a1 reverted to changing the
timestamp formatting only in development log mode, after
9ecf171 had explicitly and
unconditionally set the format to ISO-8601.

However, almost immediately after this,
5bf0440 bumped the controller-runtime
version from 0.13.1 to 0.14.5. In 0.14, the default zap options in
controller-runtime changed to RFC3339 - which is the same as ISO-8601
but even worse because subsecond precision (which can be very important
to debugging) is lost as well.

This change explicitly restores the original default.

main.go

@@ -175,6 +175,8 @@ func main() {
 	if devLogging {
 		logOpts.Development = true
 		logOpts.TimeEncoder = zapcore.ISO8601TimeEncoder
+	} else {
+		logOpts.TimeEncoder = zapcore.EpochTimeEncoder
 	}
 	ctrl.SetLogger(zap.New(zap.UseFlagOptions(&logOpts)))