Fix get_packages when $DISTRO is not set

Sourcing the tools/install-prereqs.sh script with TOP_DIR set results
in GetDistro being called in get_packages and echoing the result.
Since all output from get_packages is assumed to be package names,
this results in the attempted installation of the non-existant 'Found'
'Distro' and '[distro name]' packages.  This change removes the echo
statement to avoid this problem.

Change-Id: Idd05c31b9eec9e6209666fa16fa425cdf1f35aa2
diff --git a/functions-common b/functions-common
index 7a6c3a1..3b4309a 100644
--- a/functions-common
+++ b/functions-common
@@ -1011,7 +1011,6 @@
     fi
     if [[ -z "$DISTRO" ]]; then
         GetDistro
-        echo "Found Distro $DISTRO"
     fi
     for service in ${services//,/ }; do
         # Allow individual services to specify dependencies