Fix synchronous logon premature exit
Fix synchronous logon premature exit

When logging in, the caller is released to submit a new command before
the session is actually logged in.  Fix this by waiting for the appropriate
flag to go False.

Change-Id: I884b7da1b64c6786f673a18ee4c7d2ca69ec0bff

stackforge/pyghmi,openstack/pyghmi,openstack/pyghmi