support for s-nail (mailx replacement) syntax on el9

[aka7]

mailx pkg is no loner available on rhel9. its been replaced with s-nail, however its syntax is different.
therefore following syntax is no longer valid which is generated by aii.

env MAILRC=/dev/null from=root\@$fqdn $mailx_smtp mailx -s "\\\$subject" $rootmail

as a result failure email does not work. provide support for new format.

quick test check on cli suggests following may work

env MAILRC=/dev/null mailx -:/ -Sfrom=root@$fqdn -Smta=smtp://<smtp_address>:<port> -s "Boot record for uname -n" $rootmail