fix: adds a "ring:" prefix to ringid when placing a call

- Prior to commit e4a96e79906b5224375c8897557bbf8361fcb56e,
  newOutgoingCall would use the preferred account to place the
  call even if no uri scheme was detected in the ringId string.

- Adds a break to the end of a switch case for placing a call,
  preventing an the next case(addRingAccount) to be executed each
  call.

Change-Id: I2bce1d78eef4efe7b093b588eb47696f60c606bb
Reviewed-by: Guillaume Roguez <guillaume.roguez@savoirfairelinux.com>