Simplify Crashdump file transfer

This changes to a streambuf_iterator to read the file contents
into the response body.  It may be slightly slower, but it's
easier to read and has less opportunity for errors.

Tested:
Confirmed that a Crashdump file can be successfully downloaded
through Redfish using a browser.

Change-Id: Ic143fe4274678e89330bf354d1b8098550e8b85b
Signed-off-by: Jason M. Bills <jason.m.bills@intel.com>
diff --git a/redfish-core/lib/log_services.hpp b/redfish-core/lib/log_services.hpp
index 1b84e3b..3877541 100644
--- a/redfish-core/lib/log_services.hpp
+++ b/redfish-core/lib/log_services.hpp
@@ -2846,21 +2846,10 @@
                                                            fileName);
                             return;
                         }
-                        std::ifstream ifs(dbusFilepath, std::ios::in |
-                                                            std::ios::binary |
-                                                            std::ios::ate);
-                        std::ifstream::pos_type fileSize = ifs.tellg();
-                        if (fileSize < 0)
-                        {
-                            messages::generalError(asyncResp->res);
-                            return;
-                        }
-                        ifs.seekg(0, std::ios::beg);
-                        std::streamsize streamFileSize =
-                            static_cast<std::streamsize>(fileSize);
-                        size_t sFileSize = static_cast<size_t>(fileSize);
-                        asyncResp->res.body().resize(sFileSize, '\0');
-                        ifs.read(asyncResp->res.body().data(), streamFileSize);
+                        std::ifstream ifs(dbusFilepath,
+                                          std::ios::in | std::ios::binary);
+                        asyncResp->res.body() = std::string(
+                            std::istreambuf_iterator<char>{ifs}, {});
 
                         // Configure this to be a file download when accessed
                         // from a browser