Better v1_key not found error, plus miq_ae_password_spec

1 line of code change

1. better error message when a legacy key is not present (e.g.: missing `v1_key` throws decrypt64 error)
2. fix running specs via ./bin/rspec (5.2.x and 5.3 throw VCR errors)
3. more specs around passwords
Can we split this spec up into describe blocks for the different methods? I'm thinking something like this:
```ruby
describe ".v2_key" do
  it "finds v2_key" do
    expect(described_class.v2_key).not_to be_nil
  end
end

describe ".v1_key" do
  # ...
end

describe ".decrypt" do
  context "when decrypting with a missing encryption key" do
    #...
  end

  context "when decrypting with a valid encryption key" do
    #...
  end
end

describe ".decrypt_if_password" do
  #...
end

describe "#to_s" do
  #...
end
```

Also, don't use "should" in the ```it``` block descriptions.