eclipse-ipzilla: Make sure login was successful

If the login fails due to an invalid username or password, the only
way we can tell this is by looking at the page title and seeing if
the error message "Invalid Username or Password" is present.

If the user made a typo on their password, we shouldn't plow through
and try to run a query.  Doing so returns an HTML login page that
can't be parsed as a CSV file.

Change-Id: Ia6d7f862435a52ae09ebe29c3835bcee3cf73b93
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>