Use ConfigParser to generate tempest config

Usage of ConfigParser provides flexible way to generate various
configuration files for tempest.
Generation of a configuration file takes a time, so checking the
existence of a file is moved into function `verify`.

Blueprint tempest-verification
Closes-Bug: #1296769

Change-Id: I221bf18090e93eb66a84dc80b87c80a0d1deb99a
remove a mixed style (**{} and param=value)

There are a mixed coding style of "**{param:value}" and "key=value"
in some places. These would be misleading for following developers.
Removing this could remain a clean and clear coding style here.

Change-Id: I92df99e943f76c1c1dba4672c4b59f65ea2b1f06
show detailed exception when doing cleanup

The patch including:
* report exception information when doing cleanup
* using LOG.warning rather than LOG.info in UserGenerator
* log tenant id rather than tenant name

Change-Id: I9011f353f7995fdda143faf62b3673101c91d6a7
Merge "Use ConfigParser to generate tempest config"
Merge "remove a mixed style (**{} and param=value)"
Merge remote-tracking branch 'upstream/master'
Add boot and rebuild server scenario

Change-Id: If1fc71865372461e83a9e5e6284b3f5d6bc34259