Run processes without screen

This introduces new run_process() and screen_service() functions and sets the
groundwork to change how DevStack starts services.  screen_service() is simply a
direct call to the screen portion of the old screen_it() function and is intended
to run commands that only need to run under screen, such as log file watchers.

run_process() is a replacement for screen_it() (which remains until all of the
services are updated).  The usage is similar but requires updates to every current
screen_it() call to remove everything that requires the command to be interpreted
by a shell.

The old run_process() and _run_process() functions are still present as
old_run_process() and _old_run_process() to support the deprecated screen_it()
function.  These will all go away in the future once all services have been
confirmed to have been changed over.

There is a similar new set of stop process functions stop_process() and
screen_stop_service().  The old screen_stop() will also remain for the deprecation
period.

As an initial test/demostration this review also includes the changes for
lib/cinder to demonstrate what is required for every service.

I included the scripts I used to test this; tests/fake-service.sh and
tests/run-process.sh are quite rough around the edges and may bite.  They should
mature into productive members of the testing ecosystem someday.

Change-Id: I03322bf0208353ebd267811735c66f13a516637b
diff --git a/tests/fake-service.sh b/tests/fake-service.sh
new file mode 100755
index 0000000..d4b9b56
--- /dev/null
+++ b/tests/fake-service.sh
@@ -0,0 +1,19 @@
+#!/bin/bash
+# fake-service.sh - a fake service for start/stop testing
+# $1 - sleep time
+
+SLEEP_TIME=${1:-3}
+
+LOG=/tmp/fake-service.log
+TIMESTAMP_FORMAT=${TIMESTAMP_FORMAT:-"%F-%H%M%S"}
+
+# duplicate output
+exec 1> >(tee -a ${LOG})
+
+echo ""
+echo "Starting fake-service for ${SLEEP_TIME}"
+while true; do
+    echo "$(date +${TIMESTAMP_FORMAT}) [$$]"
+    sleep ${SLEEP_TIME}
+done
+