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.