Ensure first field render gets initial value

[kgram]

Should fix #4304, #4344 and possibly other duplicates.

Since react-redux v6, a snapshot of the state is used each render in connected components instead of the store. This makes it impossible to initialize the form before the fields render. This fix simply passes the initial value as value when the form is uninitialized.

Also fixes a number of tests that required Field to be rendered twice initially. Most notably, "Field > should have value set to initial value on first render" actually checked if the field had an initial value on the second render 😄

[kgram]

The travis-failure only occurs in node v11.11, see this issue: facebook/create-react-app#6591

I don't think there's a lot to be done about that for now.

[venondev]

@erikras Could you please have a look at this PR? We are currently facing the issue, where the values are an empty object in validate, although the initialValues exist.

[codecov-io]

Codecov Report

Merging #4397 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #4397   +/-   ##
======================================
  Coverage     100%    100%           
======================================
  Files          74      74           
  Lines        1694    1690    -4     
======================================
- Hits         1694    1690    -4

Impacted Files	Coverage Δ
src/ConnectedField.js	100% <100%> (ø)	⬆️
src/structure/immutable/deepEqual.js	100% <0%> (ø)	⬆️
src/handleSubmit.js	100% <0%> (ø)	⬆️
src/createReduxForm.js	100% <0%> (ø)	⬆️
src/structure/plain/deepEqual.js	100% <0%> (ø)	⬆️

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