contrib: dracut: inline single-use import_pool, move single-use ask_for_password

Also don't set ROOTFS_MOUNTED; the final mention was removed in dracut
011 from July 2011

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13291