* move adjustForSealMigration to vault package

* fix adjustForSealMigration

* begin working on new seal migration test

* create shamir seal migration test

* refactor testhelpers

* add VerifyRaftConfiguration to testhelpers

* stub out TestTransit

* Revert "refactor testhelpers"

This reverts commit 39593defd0d4c6fd79aedfd37df6298391abb9db.

* get shamir test working again

* stub out transit join

* work on transit join

* remove debug code

* initTransit now works with raft join

* runTransit works with inmem

* work on runTransit with raft

* runTransit works with raft

* cleanup tests

* TestSealMigration_TransitToShamir_Pre14

* TestSealMigration_ShamirToTransit_Pre14

* split for pre-1.4 testing

* add simple tests for transit and shamir

* fix typo in test suite

* debug wrapper type

* test debug

* test-debug

* refactor core migration

* Revert "refactor core migration"

This reverts commit a776452d32a9dca7a51e3df4a76b9234d8c0c7ce.

* begin refactor of adjustForSealMigration

* fix bug in adjustForSealMigration

* clean up tests

* clean up core refactoring

* fix bug in shamir->transit migration

* stub out test that brings individual nodes up and down

* refactor NewTestCluster

* pass listeners into newCore()

* simplify cluster address setup

* simplify extra test core setup

* refactor TestCluster for readability

* refactor TestCluster for readability

* refactor TestCluster for readability

* add shutdown func to TestCore

* add cleanup func to TestCore

* create RestartCore

* stub out TestSealMigration_ShamirToTransit_Post14

* refactor address handling in NewTestCluster

* fix listener setup in newCore()

* remove unnecessary lock from setSealsForMigration()

* rename sealmigration test package

* use ephemeral ports below 30000

* work on post-1.4 migration testing

* clean up pre-1.4 test

* TestSealMigration_ShamirToTransit_Post14 works for non-raft

* work on raft TestSealMigration_ShamirToTransit_Post14

* clean up test code

* refactor TestClusterCore

* clean up TestClusterCore

* stub out some temporary tests

* use HardcodedServerAddressProvider in seal migration tests

* work on raft for TestSealMigration_ShamirToTransit_Post14

* always use hardcoded raft address provider in seal migration tests

* debug TestSealMigration_ShamirToTransit_Post14

* fix bug in RestartCore

* remove debug code

* TestSealMigration_ShamirToTransit_Post14 works now

* clean up debug code

* clean up tests

* cleanup tests

* refactor test code

* stub out TestSealMigration_TransitToShamir_Post14

* set seals properly for transit->shamir migration

* migrateFromTransitToShamir_Post14 works for inmem

* migrateFromTransitToShamir_Post14 works for raft

* use base ports per-test

* fix seal verification test code

* simplify seal migration test suite

* simplify test suite

* cleanup test suite

* use explicit ports below 30000

* simplify use of numTestCores

* Update vault/external_tests/sealmigration/seal_migration_test.go
Co-authored-by: Calvin Leung Huang <cleung2010@gmail.com>

* Update vault/external_tests/sealmigration/seal_migration_test.go
Co-authored-by: Calvin Leung Huang <cleung2010@gmail.com>

* clean up imports

* rename to StartCore()

* Update vault/testing.go
Co-authored-by: Calvin Leung Huang <cleung2010@gmail.com>

* simplify test suite

* clean up tests
Co-authored-by: Calvin Leung Huang <cleung2010@gmail.com>