fix(pes_events_scanner): ensure output contains no duplicates

RpmTransactionTasks messages have higher priority than instructions
based on PES data. Previously, if multiple such messages existed
with duplicate instructions, this could lead to the crash of
the actor - especially in case when an existing package has been
asked to be removed several times. Ensure the occurance of each
instruction is unique (list -> set).

jira: RHEL-50076

repos/system_upgrade/common/actors/peseventsscanner/libraries/pes_events_scanner.py

@@ -78,19 +78,22 @@ def get_installed_pkgs():
 
 def get_transaction_configuration():
     """
-    Get pkgs to install, keep and remove from the user configuration files in /etc/leapp/transaction/.
+    Get pkgs to install, keep and remove from RpmTransactionTasks messages.
 
-    These configuration files have higher priority than PES data.
-    :return: RpmTransactionTasks model instance
+    Note these messages reflects inputs from various actors and configuration
+    files in /etc/leapp/transaction/. As these are explicit instruction, they
+    have higher priority than instructions from PES data.
+
+    :return: TransactionConfiguration
     """
-    transaction_configuration = TransactionConfiguration(to_install=[], to_remove=[], to_keep=[])
+    transaction_configuration = TransactionConfiguration(to_install=set(), to_remove=set(), to_keep=set())
 
     _Pkg = partial(Package, repository=None, modulestream=None)
 
     for tasks in api.consume(RpmTransactionTasks):
-        transaction_configuration.to_install.extend(_Pkg(name=pkg_name) for pkg_name in tasks.to_install)
-        transaction_configuration.to_remove.extend(_Pkg(name=pkg_name) for pkg_name in tasks.to_remove)
-        transaction_configuration.to_keep.extend(_Pkg(name=pkg_name) for pkg_name in tasks.to_keep)
+        transaction_configuration.to_install.update(_Pkg(name=pkg_name) for pkg_name in tasks.to_install)
+        transaction_configuration.to_remove.update(_Pkg(name=pkg_name) for pkg_name in tasks.to_remove)
+        transaction_configuration.to_keep.update(_Pkg(name=pkg_name) for pkg_name in tasks.to_keep)
     return transaction_configuration