Fix the behavior or the error message for the add_controller method.

[lsgunnlsgunn]

After setting my wallet on the alpha network, I added an identity and tried to make that second identity as a controller.
If i call the get_controllers method, my default principal is the controller of my alpha wallet:

dfx canister --network=alpha call f3yw6-7qaaa-aaaab-qaabq-cai get_controllers                      
(
 vec {
  principal "zen7w-sjxmx-jcslx-ey4hf-rfxdq-l4soz-7ie3o-hti3o-nyoma-nrkwa-cqe";
 },
)

This is expected. But I try to add the principal for my second identity while I'm the default/controller identity by running this command:

dfx canister --network=alpha call f3yw6-7qaaa-aaaab-qaabq-cai add_controller '(principal "vpqee-nujda-46rtu-4noo7-qnxmb-zqs7g-5gvqf-4gy7t-vuprx-u2urx-gqe")'

I get an error:

The Replica returned an error: code 5, message: "Canister f3yw6-7qaaa-aaaab-qaabq-cai trapped explicitly: An error happened during the call: 4: Only the controller can call this method."

This is unexpected because I've just verified that I am, in fact, the controller.

[adamspofford-dfinity]

The wallet now properly adds both itself and the caller as controllers when a canister is created, and DFX no longer automatically proxies any calls save canister creation through the wallet. This issue should be resolved upon installing the latest release of DFX.