install.sh: Add wget fallback if curl isn't available
install.sh: Add wget fallback if curl isn't available

Reportedly, some systems don't have curl but wget. With this patch,
install.sh will use wget instead of curl if the latter is not available
on the target system.

Change-Id: I0bc78feec6d8e1dbf7fbef7c2e10833b79bdbbdc
Signed-off-by: Joakim Roubert <e2b2281028c0b88d06179b6136248733ddd134cb@axis.com>

rancher/k3s,rancher/k3s