Description of problem:
When I schedule big bunch of erratas to be updated on a system using rhn_check, sometimes some of the erratas is skipped due to yum unable to acquire transaction lock.


Version-Release number of selected component (if applicable):
rhn-client-tools-1.0.0.1-8.el6.noarch
rhnlib-2.5.22-15.el6.noarch
yum-rhn-plugin-0.9.1-45.el6.noarch


How reproducible:
rarely (say, 1 of 100 rhn_check picked erratas)


Steps to Reproduce:
1. Schedule big number of erratas (I have used small custom packages)
2. On a system run `rhn_check -vv` and observe output
3. Make sure all erratas were applied (expected NVRs are installed)


Actual results:
[...]
D: logininfo:{'X-RHN-Server-Id': 1000010016, 'X-RHN-Auth-Server-Time': '1373248992.21', 'X-RHN-Auth': 'fIImq/kEChGu9K25pJnFOg==', 'X-RHN-Auth-Channels': [['parent-uwvuw', '20130707204517', '1', '1'], ['child-of-parent-uwvuw', '20130707204529', '0', '1']], 'X-RHN-Auth-User-Id': '', 'X-RHN-Auth-Expire-Offset': '3600.0'}
D: handle_action{'action': "<?xml version='1.0'?>\n<methodCall>\n<methodName>errata.update</methodName>\n<params>\n<param>\n<value><array><data>\n<value><int>771</int></value>\n</data></array></value>\n</param>\n</params>\n</methodCall>\n", 'version': 2, 'id': 131}
D: handle_action actionid = 131, version = 2
D: do_call errata.update([771],){'cache_only': None}
D: rpcServer: Calling XMLRPC errata.getErrataInfo
D: Called update[['test-arch-uwvuw-2-InChild', '0.2', '2', '', 'x86_64']]
D: Sending back response((6,), 'Error while executing packages action: Existing lock /var/run/yum.pid: another copy is running as pid 21659.', {})
D: check_action{'action': "<?xml version='1.0'?>\n<methodCall>\n<methodName>errata.update</methodName>\n<params>\n<param>\n<value><array><data>\n<value><int>773</int></value>\n</data></array></value>\n</param>\n</params>\n</methodCall>\n", 'version': 2, 'id': 132}
updateLoginInfo() login info
D: login(forceUpdate=True) invoked
[...]


Expected results:
D: Sending back response(0, 'Update Succeeded', {})


Additional info:
I'm not sure, but started to see this quite recently. Maybe it is connected with changes with bug 830219.