v.io: use test.V23Init instead of v23.Init in test code

test.V23Init creates a context that's suitable for tests, including a
test blessing and no prod mounttable root. Using test.V23Init everywhere
in tests gives us a choke-point for adding test-specific configuration
of the runtime and context.

Change-Id: I5c1a6bc4021ef83d67aa291d61a0ebd7db51d5f8
1 file changed