Build retry loop for screen sessions
Build retry loop for screen sessions

There is a timing window where we might lose the commands being
stuffed into screen because bash is spawning. In those cases, loop
around and try building screen sessions again.

Change-Id: I49247de06bbd59424cb10fb9a8db145907be5138
Related-Bug: #1331274
(cherry picked from commit 0afa912e99dc9bad8b490960beb8f0cf85750dcc)

williamthegrey/devstack