blobs/download: properly handle backup/main url

Immediately after the last revision, which was a hacky
workaround to the problem, I realised the actual problem,
and the real solution:

In the switch block, check *backup* first. Then it breaks,
continuing on the iteration.

If it's variable for a main URL, it'll reliably go to the
next check in the block, whereas if it's backup, it'll
default to the first one in each case.

This bug has been annoying the sh*t out of me for ages,
and I've finally nailed it.

Signed-off-by: Leah Rowe <leah@libreboot.org>

resources/scripts/update/blobs/download

@@ -108,14 +108,14 @@ scan_sources_config()
 
 	while read -r line ; do
 		case ${line} in
-		EC_url*)
-			set ${line}
-			ec_url=http${2##*http}
-			;;
 		EC_url_bkup*)
 			set ${line}
 			ec_url_bkup=${2}
 			;;
+		EC_url*)
+			set ${line}
+			ec_url=${2}
+			;;
 		EC_hash*)
 			set ${line}
 			ec_hash=${2}
@@ -124,26 +124,26 @@ scan_sources_config()
 			set ${line}
 			dl_hash=${2}
 			;;
-		DL_url*)
-			set ${line}
-			dl_url=http${2##*http}
-			;;
 		DL_url_bkup*)
 			set ${line}
 			dl_url_bkup=${2}
 			;;
+		DL_url*)
+			set ${line}
+			dl_url=${2}
+			;;
 		E6400_VGA_DL_hash*)
 			set ${line}
 			e6400_vga_dl_hash=${2}
 			;;
-		E6400_VGA_DL_url*)
-			set ${line}
-			e6400_vga_dl_url=http${2##*http}
-			;;
 		E6400_VGA_DL_url_bkup*)
 			set ${line}
 			e6400_vga_dl_url_bkup=${2}
 			;;
+		E6400_VGA_DL_url*)
+			set ${line}
+			e6400_vga_dl_url=${2}
+			;;
 		E6400_VGA_offset*)
 			set ${line}
 			e6400_vga_offset=${2}