[Messaging] Prevent crash of using released structure mail_data_final

[Messaging] Prevent crash of using released structure mail_data_final

In line 296, there is the usage:
  mail_data_final->thread_id = mail_data_final->mail_id;

but if retries loop above reaches limit, then the structure is relased,
so using it causes crash.
To prevent it, we release data on the beginning of the next iteration of
a loop.

[Verification] TCT passrate:
messaging-email - 100%.

Change-Id: I4751e5509271f28ab803e0ef10a90ff10d61ec10