Fixes bug#1349401:With longer user names, config tab is not available in
Contrail UI
Earlier, the width of div enclosing logged-in username is not enough to enclose bigger usernames which is making "Alerts" button to come in next row blocking the access to click on "Configure" menu button.
Increase the width of div such that "Alerts" button doesn't come in second row.

Change-Id: I99f18b13521115dacec5fc9f5ea0e882b603839b