wget: allow basic http auth for SSTATE_MIRRORS

wget: allow basic http auth for SSTATE_MIRRORS

If http basic auth creds were added to sstate mirrors like so:

https://foo.com/sstate/PATH;user=foo:bar;downloadfilename=PATH

The sstate mirror check would silently fail with 401 unauthorized.
This patch allows both the check, and the wget download to succeed by
checking for user credentials and if present adding the correct
headers, or wget params as needed.

[ YOCTO #9815 ]

Signed-off-by: Stephano Cetola <stephano.cetola@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>