Add optional retry loop to factory_Wifi test.

BUG=None
TEST=None (pending test)

(cherry picked from commit 3d143b95e5da64f747cbf9fac417d6bb2c47c7f9)

Signed-off-by: Jon Salz <jsalz@chromium.org>
Change-Id: I38b2dbd984b89e1304acc79f23bd9c03a8ec5fb5
Reviewed-on: https://gerrit.chromium.org/gerrit/24699
1 file changed