[SDFAB-285] Use stern to save a tail of pod logs

 - Only save logs from the test period
 - Fix some typos
 - Check cli connectivity after saving logs, we sometimes timed out

Change-Id: I3f62950f898bef78b6071d94bcfb17ced1a6ca45
diff --git a/TestON/tests/USECASE/SegmentRouting/dependencies/Testcaselib.py b/TestON/tests/USECASE/SegmentRouting/dependencies/Testcaselib.py
index 5f9dd8a..bc4bea6 100644
--- a/TestON/tests/USECASE/SegmentRouting/dependencies/Testcaselib.py
+++ b/TestON/tests/USECASE/SegmentRouting/dependencies/Testcaselib.py
@@ -1847,6 +1847,7 @@
         main.step( 'Set logging levels' )
         # Get original values incase we want to reset them
         ctrl = main.Cluster.active(0)
+        ctrl.CLI.clearBuffer( timeout=1 )
         ctrl.CLI.logList()
 
         logging = True
@@ -1870,6 +1871,7 @@
         main.step( 'Reset logging levels' )
         # Get original values incase we want to reset them
         ctrl = main.Cluster.active(0)
+        ctrl.CLI.clearBuffer( timeout=1 )
         currentLevels = ctrl.CLI.logList( saveValues=False )
         origLevels = ctrl.CLI.logLevels
         toBeSet = {}