An ifdef condition seems to have been inverted by mistake, causing the
dynamic initialization to occur for lite if and only if the
_NO_STATIC_INITIALIZER macro is set. This problem manifested itself as
segfaults due to uninitialized empty strings:
https://github.com/google/protobuf/issues/2839

Since no one complained about initialization not happening, it would
appear that we can just disable this initialization for lite
unconditionally, so that is what this change does. Instead of the
default instance initialization happening pre-main, it now always
happens lazily when needed.