Re-arrange the order of checks in the FL2_copyIMG to prioritise those checks with good signatures or checksums

scripts/FL2_copyIMG

@@ -626,22 +626,25 @@ sub detect_img {
 
     my $object;
     if (!defined($object)) {
-        $object = FL2::prefix_ff->new($fh);
+        $object = FL2::prefix_head_EC->new($fh);
     }
     if (!defined($object)) {
-        $object = FL2::prefix_garbage->new($fh);
+        $object = FL1::PFH_header->new($fh);
     }
     if (!defined($object)) {
-        $object = FL2::prefix_nothing->new($fh);
+        $object = FL2::prefix_head_NAPI->new($fh);
     }
+
+    # these checks have very little in the way of signatures, so only
+    # check for them after everything else
     if (!defined($object)) {
-        $object = FL2::prefix_head_EC->new($fh);
+        $object = FL2::prefix_ff->new($fh);
     }
     if (!defined($object)) {
-        $object = FL1::PFH_header->new($fh);
+        $object = FL2::prefix_garbage->new($fh);
     }
     if (!defined($object)) {
-        $object = FL2::prefix_head_NAPI->new($fh);
+        $object = FL2::prefix_nothing->new($fh);
     }
 
     return $object;