commit 7d082c03b2f4f16b31b9b54cb26bcfc added a workaround to skip
a few redraws on startup so that the intro message is not shown anymore.
However might cause problems, that some highlighting groups are not
correctly set. Also recent Vims (8.0.1290 and so on) do not seem to
suffer from the problem that an too early initializiation of airline
causes a redraw which skips the intro message.
Therefore, revert that commit.
Fixes#1585
52ce640534