qubes-anaconda-addon: clear salt minion cache before running configuration

Salt minion cache can be incomplete after initial installation. As it was
reported in #2213, just `qubesctl saltutil.sync_all` isn't enough to
refresh it in some cases - it may still lack of some files
(ext_module_qvm.py in this case). So, clear the cache completely before
initial configuration.

Fixes QubesOS/qubes-issues#2213

qubes-anaconda-addon/firstboot-qubes-text

@@ -114,6 +114,7 @@ if [ "$vms_service" == "yes" -o "$vms_app" == "yes" ]; then
         mv /var/log/salt/minion /var/log/salt/minion.install || :
     fi
 
+    qubesctl saltutil.clear_cache -l quiet --out quiet
     qubesctl saltutil.sync_all -l quiet --out quiet
 fi
 

qubes-anaconda-addon/org_qubes_os_initial_setup/gui/spokes/qubes_os.py

@@ -499,6 +499,7 @@ class QubesOsSpoke(FirstbootOnlySpokeMixIn, NormalSpoke):
             pass
 
         # Refresh minion configuration to make sure all installed formulas are included
+        self.run_command(['qubesctl', 'saltutil.clear_cache'])
         self.run_command(['qubesctl', 'saltutil.sync_all'])
 
         for state in QubesChoice.get_states():