Changes

testsuites: tunmap: trex: Set default run time to 600 seconds

Previous default of 60 was too short and I was all the time changing it
manually.

Also change the default target rate to 8275 kpps, which is aproximatelly
the amount needed to fill the 100 gbps NIC.

Change-Id: I9a20d71f542956eee08eff75eeab6a284cfdd16e