flimflam: flimflam.py: Supply Passphrase argument only when non-empty

Passing a passphrase argument to shill when the network is open
causes an error.  Don't do that.

TEST=Run connect-wifi on both open and WPA networks

Change-Id: I1f0a310360532485c83e0edde75ae1533ed97fc4
Reviewed-on: https://gerrit.chromium.org/gerrit/35579
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
1 file changed