Define 'upgrade_test' marker for tests that validate package upgrades from testing repo

Signed-off-by: Rushikesh Jadhav <rushikesh7@gmail.com>

Author: rushikeshjadhav

pytest.ini

@@ -5,6 +5,7 @@ markers =
     default_vm: mark a test with a default VM in case no --vm parameter was given.
 
     # *** Markers used to select tests at collect stage ***
+    upgrade_test: mark a test which will upgrade packages from testing repo
 
     # * Host-related markers, automatically set based on fixtures
     hostA2: a second member in the first pool.