Additional tests for pass phrase dialog for drafts

[rrrooommmaaa]

I tested this manually but would also like to create unit tests for these scenarios (in another issue)
[ ] - pressing 'close' button when trying to decrypt a draft
[ ] - pressing 'Later' when entering a pass phrase for draft decryption (as opposed to 'compose - loading drafts - PKCS#7 encrypted draft with forgotten non-primary pass phrase test) and the re-invoking the pass phrase dialog with pressing 'Pass phrase' button again

Originally posted by @rrrooommmaaa in #4109 (comment)

[tomholub]

ok with it as is