Do not show success messages

When the user performs some operations (like updating guest CD-ROMs), a green
success message is displayed on top of the screen. This behavior is not common
in Kimchi; when an operation performs successfully, nothing is shown.

In order to make Kimchi more consistent, remove the code that displays
success messages.

This patch enforces what was applied by 57f9f9f.

Signed-off-by: Crístian Viana <vianac@linux.vnet.ibm.com>
Apply Kimchi standard error message

Currently, Kimchi uses different ways of displaying error messages.

Use the standard message (kimchi.message) to display HTML errors.

This is one step towards the solution of issue #215.

Signed-off-by: Crístian Viana <vianac@linux.vnet.ibm.com>
Display the error code when displaying error msgs

Error messages which are associated to error codes should display
their error codes as well, in order to make problems
identification easier.

Use a different error function to display the error code in the
error message.

Signed-off-by: Crístian Viana <vianac@linux.vnet.ibm.com>