iotests: Add -o and --no-opts to _make_test_img

Blindly overriding IMGOPTS is suboptimal as this discards user-specified
options.  Whatever options the test needs should simply be appended.

Some tests do this (with IMGOPTS=$(_optstr_add "$IMGOPTS" "...")), but
that is cumbersome.  It’s simpler to just give _make_test_img an -o
parameter with which tests can add options.

Some tests actually must override the user-specified options, though,
for example when creating an image in a different format than the test
$IMGFMT.  For such cases, --no-opts allows clearing the current option
list.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-id: 20191107163708.833192-10-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

tests/qemu-iotests/common.rc

@@ -308,6 +308,7 @@ _make_test_img()
     local use_backing=0
     local backing_file=""
     local object_options=""
+    local opts_param=false
     local misc_params=()
 
     if [ -n "$TEST_IMG_FILE" ]; then
@@ -328,6 +329,10 @@ _make_test_img()
         if [ "$use_backing" = "1" -a -z "$backing_file" ]; then
             backing_file=$param
             continue
+        elif $opts_param; then
+            optstr=$(_optstr_add "$optstr" "$param")
+            opts_param=false
+            continue
         fi
 
         case "$param" in
@@ -335,6 +340,14 @@ _make_test_img()
                 use_backing=1
                 ;;
 
+            -o)
+                opts_param=true
+                ;;
+
+            --no-opts)
+                optstr=""
+                ;;
+
             *)
                 misc_params=("${misc_params[@]}" "$param")
                 ;;