make USE_SCREEN=False imply USE_SYSTEMD=True

In order to start making the transition in the gate make
USE_SCREEN=False also mean USE_SYSTEMD=True. We'll never actually
declare USE_SYSTEMD=True in the gate (as that doesn't exist for stable
branches), but this will let us roll over the existing transition.

We also have to install systemd-python 234 because we are recording
exception info in the journal, and all versions before that had a bug
in processing that.

Remove the somewhat pointless screen following journalctl commands. We
really don't want or need those, and they tend to build up over time.

Depends-On: I24513f5cbac2c34cf0130bf812ff2df6ad76657c

Change-Id: I6af6d1857effaf662a9d72bd394864934eacbe70
diff --git a/stackrc b/stackrc
index ed1cf6e..6ff9585 100644
--- a/stackrc
+++ b/stackrc
@@ -157,6 +157,15 @@
     source $RC_DIR/.localrc.auto
 fi
 
+# if we are forcing off USE_SCREEN (as we do in the gate), force on
+# systemd. This allows us to drop one of 3 paths through the code.
+if [[ "$USE_SCREEN" == "False" ]]; then
+    # Remove in Pike: this gets us through grenade upgrade
+    if [[ "$GRENADE_PHASE" != "target" ]]; then
+        USE_SYSTEMD="True"
+    fi
+fi
+
 # Default for log coloring is based on interactive-or-not.
 # Baseline assumption is that non-interactive invocations are for CI,
 # where logs are to be presented as browsable text files; hence color