meta-gsj: fix do_install for usrmerge

The recipe previously had a hard coded removal of `/lib` which will no
longer exist under usrmerge.  I think the purpose of this was to delete
the systemd units, but leave the library.  Therefore I've adjusted the
removal to be systemd_unitdir instead of `/lib`.

This results in the following package structure:
```
$ find tmp/work/armv7a-openbmc-linux-gnueabi/google-ipmi-sys/0.1+gitAUTOINC+59445f5e21-r1/packages-split/google-ipmi-sys -type f
tmp/work/armv7a-openbmc-linux-gnueabi/google-ipmi-sys/0.1+gitAUTOINC+59445f5e21-r1/packages-split/google-ipmi-sys/usr/lib/systemd/system-preset/98-google-ipmi-sys.preset
tmp/work/armv7a-openbmc-linux-gnueabi/google-ipmi-sys/0.1+gitAUTOINC+59445f5e21-r1/packages-split/google-ipmi-sys/usr/lib/ipmid-providers/libgooglesys.so
```

The `98-google-ipmi-sys.preset` file is empty.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I05dd016fcc8dfd8dc33ba90acad100afafb18073
diff --git a/meta-quanta/meta-gsj/recipes-google/ipmi/google-ipmi-sys_%.bbappend b/meta-quanta/meta-gsj/recipes-google/ipmi/google-ipmi-sys_%.bbappend
index 90200fe..651cf2d 100644
--- a/meta-quanta/meta-gsj/recipes-google/ipmi/google-ipmi-sys_%.bbappend
+++ b/meta-quanta/meta-gsj/recipes-google/ipmi/google-ipmi-sys_%.bbappend
@@ -6,5 +6,5 @@
   "
 
 do_install:append:gsj() {
-   rm -r ${D}/lib
+   rm -r ${D}${systemd_unitdir}
 }