Move snippet suggestions above keywords in completion list

[hopehadfield]

Fixes redhat-developer/vscode-java#2584

Before:

After:

[rgrunber]

As a note, the behaviour here is a client-side issue (it's arguable whether it's a feature or not). Basically, the language server correctly uses sortText to place the if keyword item at the bottom. However, since the if keyword fully matches what the client is filtering on (if), those matching items seem to prioritized.