qemu-iotests: fix uninitialized variable

The variable is used in "common" but defined only after the file
is sourced.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/check

@@ -77,8 +77,6 @@ fi
 
 TIMESTAMP_FILE=check.time-$IMGPROTO-$IMGFMT
 
-tmp="${TEST_DIR}"/$$
-
 _wallclock()
 {
     date "+%H %M %S" | awk '{ print $1*3600 + $2*60 + $3 }'

tests/qemu-iotests/common

@@ -67,6 +67,8 @@ sortme=false
 expunge=true
 have_test_arg=false
 cachemode=false
+
+tmp="${TEST_DIR}"/$$
 rm -f $tmp.list $tmp.tmp $tmp.sed
 
 export IMGFMT=raw