Do players play "boring" openings before an important tournament? The London Chess Classic is being held at the moment, just three months away from the Candidates, with some of the best players of the world and 6 of the participants of the candidates (Giri, Nakamura, Topalov, Anand, Caruana and Aronian).

So far the openings have been a bit "dull" in the majority of the games without any really sharp line or theoretical novelty. I feel that in the previous stages of the Grand Chess Tour the openings were much more sharper and fun to watch as an spectator.

Might this be caused because the Candidates is really close and the players don't want to show their preparation or is it just a coincidence? Is it usual for the players to play "boring" and well known lines before a big tournament?
"Hiding prep'" is a well known cliche in the chess world. When Anand had a slump in form a few years back, it was joked that he has been hiding his preparation for several years now. 

I believe there are two sides to this phenomenon:

Especially going into world championship matches, players sometimes revamp complete parts of their opening repertoire. For example Leko going for 1.d4 against Kramnik, or Gelfand taking up the Sveshnikov and Grunfeld against Anand, or Kramnik playing the Berlin against Kasparov … Obviously in these cases the whole purpose of the preparation would have been defeated if they had tried the lines in some preliminary tournament. 

On the other hand, if a top player doesn't plan to spring such a big surprise, arguably it doesn't make too much sense to hide single novelties or variations from your opponents. After all in every single game only the tiniest part of the preparation of a top GM is revealed. Showing one tricky line doesn't rip a big hole into your repertoire and you never know whether anybody will walk into your trap again. GM Gustafsson has repeatedly argued that even right before very important tournaments, top GMs are happy to spring a trap before a different player grabs that opportunity, after all they are all using the same engines ...