Wait for OVS to reconfigure when creating PUBLIC_BRIDGE

The '--no-wait' flag will not wait for ovs-vswitchd to reconfigure after
changes have been made to the database. This causes a race condition as
the bridge may or may not be up when 'ip addr flush dev $PUBLIC_BRIDGE' is
called. This commit removes the '--no-wait' flag which is safe as the
openvswitch services are already started earlier in stack.sh

Change-Id: I73ef1b731295d03b0f064c5f786196284c3e39ce
Closes-bug: #1328962
Fix unsubstituted filename creation

Since merge_config_file() tries to create an unsubstituted config file,
stack.sh fails due to permission denied in the file creation when you
use '[[post-config|/$Q_PLUGIN_CONF_FILE]]' and the file does not exist.

This patch deletes unnecessary 'touch' command, because the file will
be made by 'iniset' function in the next command line with evaled
string from 'configfile'.

This patch also fixes merge_config_group() to use evaled 'configfile'
when it checks the directory of the config file exists.

Change-Id: I608847a34143b5c6a1708c180186dd88a32dd44b
Closes-bug: #1294213
Merge "Wait for OVS to reconfigure when creating PUBLIC_BRIDGE"
Merge "Fix unsubstituted filename creation"