pgsql: In ipcclean, check LOGNAME only if USER is not set.

Log Message:
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In ipcclean, check LOGNAME only if USER is not set.

Fixes problem with 'su' on some platforms.

Modified Files:
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pgsql/src/bin/ipcclean:
ipcclean.sh (r1.16 -> r1.17)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/ipcclean/ipcclean.sh.diff?r1=1.16&r2=1.17)