Description of problem:
Failed to move app which is created from downloadable cartridge due to httpd.pid file is empty.

Version-Release number of selected component (if applicable):
devenv_3953

How reproducible:
always

Steps to Reproduce:
1.create an app from a downloadable cartridge.
#  rhc app create app2 https://raw.github.com/zhaozhanqi/phpv2/master/metadata/manifest.yml
2.move this app.
3.on node, truncate httpd.pid file for this app.
4.move this app.

Actual results:
Step 2, move successfully.
Step 4,
# oo-admin-move --gear_uuid 526e18c760aeeaccd1000001 -i ip-10-239-15-81
URL: http://app2-lxia.dev.rhcloud.com
Login: lxia
App UUID: 526e18c760aeeaccd1000001
Gear UUID: 526e18c760aeeaccd1000001
DEBUG: Source district uuid: 3f5e62d03f7911e3aa0122000a49841d
DEBUG: Destination district uuid: 3f5e62d03f7911e3aa0122000a49841d
DEBUG: Getting existing app 'app2' status before moving
DEBUG: Gear component 'zhaozhanqi-php-5.3' was running
DEBUG: Stopping existing app cartridge 'zhaozhanqi-php-5.3' before moving
DEBUG: Error performing stop on existing app on try 1: Node execution failure (invalid exit code from node).
DEBUG: Error performing stop on existing app on try 2: Node execution failure (invalid exit code from node).
DEBUG: Force stopping existing app cartridge 'zhaozhanqi-php-5.3' before moving
DEBUG: Creating new account for gear 'app2' on ip-10-239-15-81
DEBUG: Moving content for app 'app2', gear 'app2' to ip-10-239-15-81
Identity added: /var/www/openshift/broker/config/keys/rsync_id_rsa (/var/www/openshift/broker/config/keys/rsync_id_rsa)
Agent pid 19888
unset SSH_AUTH_SOCK;
unset SSH_AGENT_PID;
echo Agent pid 19888 killed;
DEBUG: Moving system components for app 'app2', gear 'app2' to ip-10-239-15-81
Identity added: /var/www/openshift/broker/config/keys/rsync_id_rsa (/var/www/openshift/broker/config/keys/rsync_id_rsa)
Agent pid 19951
unset SSH_AUTH_SOCK;
unset SSH_AGENT_PID;
echo Agent pid 19951 killed;
DEBUG: Starting cartridge 'zhaozhanqi-php-5.3' in 'app2' after move on ip-10-239-15-81
DEBUG: Moving failed.  Rolling back gear 'app2' in 'app2' with delete on 'ip-10-239-15-81'
Node execution failure (invalid exit code from node).

Expected results:
App should be moved successfully when cartridge's httpd.pid file is empty.

Additional info:
Move app with empty httpd.pid file can success if not using download cartridge.