cdrom_id: suppress ID_CDROM_MEDIA_STATE=blank for plain non-writable CDROM media

cdrom_id: suppress ID_CDROM_MEDIA_STATE=blank for plain non-writable CDROM media

Some broken fake cdrom drives return ID_CDROM_MEDIA_STATE=blank.

  $ /lib/udev/cdrom_id -d /dev/sr1
  main: probing: '/dev/sr1'
  cd_inquiry: INQUIRY: [Nokia   ][S60             ][1.0 ]
  cd_profiles: GET CONFIGURATION: number of profiles 76
  cd_profiles: current profile 0x08
  cd_media_toc: READ TOC: len: 12
  cd_media_toc: last track 1 starts at block 0
  cd_media_info: disk type 00
  ID_CDROM=1
  ID_CDROM_MRW=1
  ID_CDROM_MRW_W=1
  ID_CDROM_MEDIA=1
  ID_CDROM_MEDIA_CD=1
  ID_CDROM_MEDIA_STATE=blank

Others work fine, but ID_CDROM_MEDIA_STATE is not needed for non-writable CDROM media:

  $ /lib/udev/cdrom_id -d /dev/sr1
  main: probing: '/dev/sr1'
  cd_inquiry: INQUIRY: [SanDisk ][U3 Cruzer Micro ][8.02]
  cd_profiles: GET CONFIGURATION: number of profiles 72
  cd_profiles: current profile 0x08
  cd_media_toc: READ TOC: len: 20
  cd_media_toc: track=1 info=0x4(data) start_block=0
  cd_media_toc: last track 1 starts at block 0
  cd_media_info: disk type 00
  ID_CDROM=1
  ID_CDROM_MRW=1
  ID_CDROM_MRW_W=1
  ID_CDROM_MEDIA=1
  ID_CDROM_MEDIA_CD=1
  ID_CDROM_MEDIA_STATE=complete
  ID_CDROM_MEDIA_SESSION_COUNT=1
  ID_CDROM_MEDIA_TRACK_COUNT=1
  ID_CDROM_MEDIA_TRACK_COUNT_DATA=1