Persist reply mode when switching to secure forward

[sosnovsky]

When switching to secure forward using this red banner, it switches to secure reply but should persist forward mode:

steps to reproduce:

• open thread with encrypted message
• click ... button in top right corner of encrypted message
• click Forward in the message menu
• compose box appears with red banner
• click Switch to encrypted compose
• it switches to secure reply, but should be secure forward

In 8.5.6 release it worked correctly, probably caused by some changes in our latest release.
Also need to add test for this case, to avoid similar issues in the next releases.

[sosnovsky]

Hi @ioanmo226, can you please work on this and #5906 issues.
It's 2 regressions found by customer in the latest 8.5.8 release, which were not present in the previous releases.

Can be caused by 9a50933, as there we've changed some code related to replies.