indirect installer: Use curl instead of wget

wget 1.12 on Chromium OS < 5116 (R33) is buggy and not able to
fetch the latest installer.

Also, use direct URL as curl does not follow redirections.
indirect installer: Fix curl fetching

Add -L so that curl follows redirection. Also, increase maximum
download time to 5 minutes in case the crouton installer grows
in size, but keep a 60 seconds connect timeout.

Finally, add -# so that the user is informed of the download
progress (again, more useful if crouton ever becomes larger).

Tested on a very old x86-zgb image 4100.89.0: curl behaves correctly.
Merge branch 'indirect-use-curl' of https://github.com/drinkcat/chroagh