[pam-ipmi]: fix default data file permissions

Use install-data-hook to set correct permissions on the data files. The
default data file is installed as 0644, and these two files need 0600.

Tested: checked that the files get installed as 0600

Change-Id: Ie93104f5f6c8df6903c8b52b276af3f217f54263
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/Makefile.am b/Makefile.am
index dc69bc8..850d6f3 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -3,6 +3,10 @@
 CLEANFILES = *~
 
 sysconf_DATA = key_file ipmi_pass
+install-data-hook:
+	chmod 0600 $(DESTDIR)$(sysconfdir)/key_file
+	chmod 0600 $(DESTDIR)$(sysconfdir)/ipmi_pass
+
 securelibdir = /lib/security
 securelib_LTLIBRARIES = pam_ipmicheck.la pam_ipmisave.la