[remoting mac host] Fix host executable path in postflight.

The host installer package was trying to run the config-upgrade tool
using the wrong path to the host binary.

Bug: 970029
Change-Id: I1d63c0151343ef6fa8e45c7d56663c29ef6754f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1642129
Commit-Queue: Lambros Lambrou <lambroslambrou@chromium.org>
Commit-Queue: Joe Downing <joedow@chromium.org>
Auto-Submit: Lambros Lambrou <lambroslambrou@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665697}

remoting/host/installer/mac/Scripts/remoting_postflight.sh

@@ -16,7 +16,7 @@ PAM_CONFIG=/etc/pam.d/chrome-remote-desktop
 ENABLED_FILE="$HELPERTOOLS/$SERVICE_NAME.me2me_enabled"
 ENABLED_FILE_BACKUP="$ENABLED_FILE.backup"
 HOST_BUNDLE_NAME=@@HOST_BUNDLE_NAME@@
-HOST_EXE=$CONFIG_DIR/$HOST_BUNDLE_NAME/Contents/MacOS/remoting_me2me_host
+HOST_EXE="$HELPERTOOLS/$HOST_BUNDLE_NAME/Contents/MacOS/remoting_me2me_host"
 
 KSADMIN=/Library/Google/GoogleSoftwareUpdate/GoogleSoftwareUpdate.bundle/Contents/MacOS/ksadmin
 KSUPDATE=https://tools.google.com/service/update2