insert-file-contents from seekable non-regular

insert-file-contents from seekable non-regular

* src/fileio.c (Finsert_file_contents): Be more conservative
when reading from seekable non-regular files when END is given.
The code assumed that in this case, reads would succeed or fail
quickly so there was no need to call internal_condition_case_1.
However, in some cases, e.g., /dev/random, it could take a while.
This fixes a glitch introduced in commit
cb4579ed6ba45c81ee7ec627bf197e1def121f24 dated 2022-06-11.

(cherry picked from commit aaf9c5213f7102dca8da7b6aaf1d400419eda075)