Fix unwanted deletion of record/replay files

Fix unwanted deletion of record/replay files
https://bugs.webkit.org/show_bug.cgi?id=166040

Reviewed by Alex Christensen.

As part of some refactoring, the objects that create the meta files
that are part of the record/replay cache would get deleted. They were
always getting opened in "write" mode", which would truncate the
files. Fix this so that the files are opened in the right modes for
record, replay, and neither.

* NetworkProcess/capture/NetworkCaptureManager.cpp:
(WebKit::NetworkCapture::Manager::initialize):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@210005 268f45cc-cd09-0410-ab3c-d52691b4dbfc