I'll try to explain warnings. Sorry, if many tech. terms.
Need special selinux contexts for plesk correct working. Especcialy it affected mail system.
Native system package selinux-policy-targeted contains definition for qmail (check file /usr/share/selinux/targeted/qmail.pp.bz2), but context is not correct, so psa-selinux installs properly context.
If U will update system package selinux-policy-targeted during postinstall stage it tries to apply default qmail context (and many other), but such context is already exists (semodule -l | grep plesk). So there is policy conflict and selinux-policy-targeted skip qmail context installation, note all another policy are installed well.
[root@a10-52-42-34 targeted]# semodule -i qmail.pp.bz2 -s targeted
/etc/selinux/targeted/contexts/files/file_contexts: Multiple different specifications for /var/qmail/queue(/.*)? (system_u

bject_r:qmail_spool_t:s0 and system_u

bject_r:mail_spool_t:s0).
/etc/selinux/targeted/contexts/files/file_contexts: Multiple different specifications for /var/qmail/control(/.*)? (system_u

bject_r:qmail_etc_t:s0 and system_u

bject_r:etc_mail_t:s0).
/etc/selinux/targeted/contexts/files/file_contexts: Multiple different specifications for /var/qmail/bin/tcp-env (system_u

bject_r:qmail_tcp_env_exec_t:s0 and system_u

bject_r:sendmail_exec_t:s0).
/etc/selinux/targeted/contexts/files/file_contexts: Multiple different specifications for /var/qmail/bin/qmail-smtpd (system_u

bject_r:qmail_smtpd_exec_t:s0 and system_u

bject_r:sendmail_exec_t:s0).
/etc/selinux/targeted/contexts/files/file_contexts: Invalid argument
libsemanage.semanage_install_active: setfiles returned error code 1.
/etc/selinux/targeted/contexts/files/file_contexts: Multiple different specifications for /var/qmail/queue(/.*)? (system_u

bject_r:qmail_spool_t:s0 and system_u

bject_r:mail_spool_t:s0).
/etc/selinux/targeted/contexts/files/file_contexts: Multiple different specifications for /var/qmail/control(/.*)? (system_u

bject_r:qmail_etc_t:s0 and system_u

bject_r:etc_mail_t:s0).
/etc/selinux/targeted/contexts/files/file_contexts: Multiple different specifications for /var/qmail/bin/tcp-env (system_u

bject_r:qmail_tcp_env_exec_t:s0 and system_u

bject_r:sendmail_exec_t:s0).
/etc/selinux/targeted/contexts/files/file_contexts: Multiple different specifications for /var/qmail/bin/qmail-smtpd (system_u

bject_r:qmail_smtpd_exec_t:s0 and system_u

bject_r:sendmail_exec_t:s0).
/etc/selinux/targeted/contexts/files/file_contexts: Invalid argument
libsemanage.semanage_install_active: setfiles returned error code 1.
semodule: Failed!
[root@a10-52-42-34 targeted]# echo $?
1
[root@a10-52-42-34 targeted]#
[root@a10-52-42-34 targeted]# semodule -l | egrep "plesk|qmail"
plesk 9.5.4 <<< incrrorect policy are not applied
[root@a10-52-42-34 targeted]#
So warnings just show that properly plesk-selinux contexts are not rewriten.