clean up logging around run_process

We do a bunch of exec magic unwind in run_process that leads to a lot
of confusing lines in the logs under xtrace. Instead, disable xtrace
through these parts to ensure that the flow at the end of the day
makes more sense.

Change-Id: I91e02465240e704a1a0c0036f5073c0295be018e

Author: sdague

functions-common

@@ -1137,6 +1137,10 @@ function zypper_install {
 # the command.
 # _run_process service "command-line" [group]
 function _run_process {
+    # disable tracing through the exec redirects, it's just confusing in the logs.
+    xtrace=$(set +o | grep xtrace)
+    set +o xtrace
+
     local service=$1
     local command="$2"
     local group=$3
@@ -1160,6 +1164,9 @@ function _run_process {
         export PYTHONUNBUFFERED=1
     fi
 
+    # reenable xtrace before we do *real* work
+    $xtrace
+
     # Run under ``setsid`` to force the process to become a session and group leader.
     # The pid saved can be used with pkill -g to get the entire process group.
     if [[ -n "$group" ]]; then