initial work to enable systemd service running

During the PTG there was a discussion that the screen developer
workflow wasn't nearly as useful as it once was. There were now too
many services to see them all on one screen, and one of the most
common service restart scenarios was not restarting one service, but a
bunch to get code to take effect.

This implements a 3rd way of running services instead of direct
forking via bash, or running under screen, which is running as systemd
units.

Logging is adjusted because it's redundant to log datetime in oslo.log
when journald has that.

Swift needed to have services launched by absolute path to work.

This is disabled by default, but with instructions on using it. The
long term intent is to make this the way to run devstack, which would
be the same between both the gate and local use.

Some changes were also needed to run_process to pass the run User
in. A hack around the keystone uwsgi launcher was done at the same
time to remove a run_process feature that only keystone uwsgi uses.

Change-Id: I836bf27c4cfdc449628aa7641fb96a5489d5d4e7

lib/dstat

@@ -24,12 +24,12 @@ function start_dstat {
     # To enable memory_tracker add:
     #    enable_service memory_tracker
     # to your localrc
-    run_process memory_tracker "sudo $TOP_DIR/tools/memory_tracker.sh"
+    run_process memory_tracker "$TOP_DIR/tools/memory_tracker.sh" "" "root"
 
     # remove support for the old name when it's no longer used (sometime in Queens)
     if is_service_enabled peakmem_tracker; then
         deprecated "Use of peakmem_tracker in devstack is deprecated, use memory_tracker instead"
-        run_process peakmem_tracker "sudo $TOP_DIR/tools/memory_tracker.sh"
+        run_process peakmem_tracker "$TOP_DIR/tools/memory_tracker.sh" "" "root"
     fi
 }