[OpenJDK 2D-Dev] RFR: 8146881: [TEST] update some imageio plugins tests to affect TIFF format

[Alexander Stepanov]

Hello,

Some imageio plugins reg. tests should probably be updated to reflect 
the fact that TIFF format is supported now.

Could you please let me know if the following changes are appropriate?
http://cr.openjdk.java.net/~avstepan/8146881/webrev.00/index.html
(bug: https://bugs.openjdk.java.net/browse/JDK-8146881)

Thanks,
Alexander