I'm signing raw transaction with signrawtransaction using bitcoin-cli (Bitcoin Core).

Even if you repeat the same transaction, each signature should be created with a different random value k which gives the first part of the signature (r).

 I'm sure this is what happens once a transaction is sent (otherwise there would be massive theft), but in the command line, when I call signrawtransaction more than once for the same transaction I always get the same signature.  I would like to generate different valid signatures for the same transaction. 

So, when/how does the client decide it is time for a new value of k? Should I create some code to sign my transactions from scratch or is there a way to force a new k using signrawtransaction?