Update comments to reflect current USE_SCREEN usage

In a couple of places the tracking of USE_SCREEN has drifted from the
comments.

Correct that.

Change-Id: I63bdd5ca4de49bf653f5bc8f8e0e5efe67ef605c

Author: tbreeds

functions-common

@@ -1352,6 +1352,7 @@ function is_running {
 # If the command includes shell metachatacters (;<>*) it must be run using a shell
 # If an optional group is provided sg will be used to run the
 # command as that group.
+# Uses globals ``USE_SCREEN``
 # run_process service "command-line" [group]
 function run_process {
     local service=$1
@@ -1370,7 +1371,7 @@ function run_process {
 
 # Helper to launch a process in a named screen
 # Uses globals ``CURRENT_LOG_TIME``, ```LOGDIR``, ``SCREEN_LOGDIR``, `SCREEN_NAME``,
-# ``SERVICE_DIR``, ``USE_SCREEN``, ``SCREEN_IS_LOGGING``
+# ``SERVICE_DIR``, ``SCREEN_IS_LOGGING``
 # screen_process name "command-line" [group]
 # Run a command in a shell in a screen window, if an optional group
 # is provided, use sg to set the group of the command.
@@ -1381,7 +1382,6 @@ function screen_process {
 
     SCREEN_NAME=${SCREEN_NAME:-stack}
     SERVICE_DIR=${SERVICE_DIR:-${DEST}/status}
-    USE_SCREEN=$(trueorfalse True USE_SCREEN)
 
     screen -S $SCREEN_NAME -X screen -t $name
 
@@ -1465,14 +1465,13 @@ function screen_rc {
 # If a PID is available use it, kill the whole process group via TERM
 # If screen is being used kill the screen window; this will catch processes
 # that did not leave a PID behind
-# Uses globals ``SCREEN_NAME``, ``SERVICE_DIR``, ``USE_SCREEN``
+# Uses globals ``SCREEN_NAME``, ``SERVICE_DIR``
 # screen_stop_service service
 function screen_stop_service {
     local service=$1
 
     SCREEN_NAME=${SCREEN_NAME:-stack}
     SERVICE_DIR=${SERVICE_DIR:-${DEST}/status}
-    USE_SCREEN=$(trueorfalse True USE_SCREEN)
 
     if is_service_enabled $service; then
         # Clean up the screen window
@@ -1490,7 +1489,6 @@ function stop_process {
     local service=$1
 
     SERVICE_DIR=${SERVICE_DIR:-${DEST}/status}
-    USE_SCREEN=$(trueorfalse True USE_SCREEN)
 
     if is_service_enabled $service; then
         # Kill via pid if we have one available
@@ -1552,11 +1550,11 @@ function service_check {
 }
 
 # Tail a log file in a screen if USE_SCREEN is true.
+# Uses globals ``USE_SCREEN``
 function tail_log {
     local name=$1
     local logfile=$2
 
-    USE_SCREEN=$(trueorfalse True USE_SCREEN)
     if [[ "$USE_SCREEN" = "True" ]]; then
         screen_process "$name" "sudo tail -f $logfile"
     fi

stackrc

@@ -101,7 +101,7 @@ HORIZON_APACHE_ROOT="/dashboard"
 # ctrl-c, up-arrow, enter to restart the service. Starting services
 # this way is slightly unreliable, and a bit slower, so this can
 # be disabled for automated testing by setting this value to False.
-USE_SCREEN=True
+USE_SCREEN=$(trueorfalse True USE_SCREEN)
 
 # When using screen, should we keep a log file on disk?  You might
 # want this False if you have a long-running setup where verbose logs