Added ifdefs for complete_SSL_shutdown

Submitted on the forums by user mdaniel ( /v\atthew ):
http://support.nagios.com/forum/viewtopic.php?t=27027#p97817
Merge branch 'nossl_fix' of https://github.com/abrist/nrpe into abrist-nossl_fix
Merge branch 'abrist-nossl_fix'