Fix zfs.spec.in defaults

Commit 2ee4e7d accidentally introduced two issues which only occur
when rebuilding the ZFS source rpm outside the ZFS build system.

1) The _dracutdir, _udevdir, and _udevruledir macros must be checked
   using the 'undefined' keyword.  This was just overlooked in the
   patch review and does not cause a failure when using 'make pkg'
   because the values are provided by the make target.

2) The default _udevruledir path included a typo.

Signed-off-by: Brian Behlendorf <[email protected]>
Issue openzfs#2310

rpm/generic/zfs.spec.in

@@ -2,7 +2,7 @@
 %global _libdir     /%{_lib}
 
 # Set the default udev directory based on distribution.
-%if 0%{!?_udevdir}
+%if %{undefined _udevdir}
 %if 0%{?fedora} >= 17 || 0%{?rhel} >= 7 || 0%{?centos} >= 7
 %global _udevdir    %{_prefix}/lib/udev
 %else
@@ -11,16 +11,16 @@
 %endif
 
 # Set the default udevrule directory based on distribution.
-%if 0%{!?_udevruledir}
+%if %{undefined _udevruledir}
 %if 0%{?fedora} >= 17 || 0%{?rhel} >= 7 || 0%{?centos} >= 7
-%global _udevruledir    %{_prefix}/lib/udevrule/rules.d
+%global _udevruledir    %{_prefix}/lib/udev/rules.d
 %else
-%global _udevruledir    /lib/udevrule/rules.d
+%global _udevruledir    /lib/udev/rules.d
 %endif
 %endif
 
 # Set the default dracut directory based on distribution.
-%if 0%{!?_dracutdir}
+%if %{undefined _dracutdir}
 %if 0%{?fedora} >= 17 || 0%{?rhel} >= 7 || 0%{?centos} >= 7
 %global _dracutdir  %{_prefix}/lib/dracut
 %else