support/download: rename internal 'verbose' variable where applicable

support/download: rename internal 'verbose' variable where applicable

Most 'verbose' variable inside the download helpers actually mean 'quiet'.
I.e. they are assigned in case quiet operation is requested, and empty in
case of non-quiet operation. Using the name 'verbose' for such a variable is
confusing, especially when you want to test the variable on emptiness or
non-emptiness (in a subsequent commit).

Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>