CLOUDSTACK-7645: [UI] Fixed incorrect label issues caused the dictionary split

In some cases the UI does not display the correct text, displaying 'label.xyz' instead of the localized string.
This appears to be due to the dictionary split: entries in dictionary2.jsp are not found because the dictionary has not been extended with dictionary2 as expected.

In this fix:
- Instead of extending the dictionary, we leave it as it is and change the localization function to look in the dictionary first and, if the item is not found there, then look in dictionary2.
- This way we are not depending on the extent() function to be called at the 'right' time; In turn, the localization function will be aware of both dictionaries.
- In the future, when we add another dictionary, we will have to modify this function only.
CLOUDSTACK-7831: Fixed unlocalized string on Advanced Network -> Network tab
CLOUDSTACK-7318: [UI] Add error handler for VM snapshot creation

Fixes the issue where processing wheel continue to spin even after error
message is displayed during VM snapshot creation