Fix timing issue when writing container stdout to the host
Fix timing issue when writing container stdout to the host

This issue was detected when running the tests against go tip.

SUSE/zypper-docker,SUSE/zypper-docker,mssola/zypper-docker,mssola/zypper-docker,SUSE/zypper-docker,jloehel/zypper-docker,jloehel/zypper-docker,jloehel/zypper-docker,mssola/zypper-docker,mssola/zypper-docker