1) Fixing the issues while applying platform TxCTLE settings in sfputil.py for QFX5200
2) Adding the support for transceiver dom threshold info in sfputil.py for both QFX5210 & QFX5200 platforms
3) Updating the sfputil.py for QFX5210 & QFX5200 platforms
4) Adding a new platform specific command 'show_thresholds' to display the FAN dutycycle percentage for various temperature ranges (for both AFI & AFO QFX5200 systems).
Signed-off-by: Ciju Rajan K <crajank@juniper.net>
