run: improve -drive file quoting to be saner

Author: cirosantilli

run

@@ -229,7 +229,7 @@ ${vnc}"
     root='root=/dev/anything'
   else
     if [ ! "$arch" = mips64 ]; then
-      extra_flags="${extra_flags} -drive file='${images_dir}/rootfs.ext2.qcow2,if=virtio,format=qcow2' \\
+      extra_flags="${extra_flags} -drive 'file=${images_dir}/rootfs.ext2.qcow2,if=virtio,format=qcow2' \\
 "
       root='root=/dev/vda'
     fi
@@ -279,7 +279,7 @@ ${extra_flags} \
     mips64)
       if ! "$ramfs"; then
         root='root=/dev/hda'
-        extra_flags="${extra_flags} -drive file='${images_dir}/rootfs.ext2.qcow2,format=qcow2' \\
+        extra_flags="${extra_flags} -drive 'file=${images_dir}/rootfs.ext2.qcow2,format=qcow2' \\
 "
       fi
       cmd="\