Fix override of defaultValue in FormInput

[JulienMattiussi]

Issue

Issue introduced by the persistency of the empty filters that was implemented.

defaultValue of a FormInput can be set by mistake if this situation :

• Add a displayed filter containing a defaultValue in your list
• Clean it's value (but don't remove the filter)
• Navigate elsewere
• Come back in the initial list
  => The defaultValue has been set again, and the filter is "un-removable"

Solution

Ignore defaultValue in Field because it is always set at Form level

Notes

final-form/react-final-form#387