Teleport to a region with a different voice server type causes failure in voice

When teleporting, the viewer 'hides' voice, effectively disabling it, until the teleport
has completed.  It does this by instructing the voice module to hide and then unhide.

The problem was, it would instruct one voice module for one voice server type to hide,
and then after teleport, it would instruct the other voice module for the other voice
server type to unhide, resulting in one voice module being hidden.

When the user transitions back to a region with the initial voice module, it's hidden,
hence voice doesn't work.

The solution is to hide/unhide both voice modules.