Remove backup files generated by sed

Change-Id: I803320fac2bbb8852449d175e986a9f63e7cdbfe
diff --git a/tools/package/onos-prep-karaf b/tools/package/onos-prep-karaf
index 658c8d2..6564d5f 100755
--- a/tools/package/onos-prep-karaf
+++ b/tools/package/onos-prep-karaf
@@ -28,7 +28,7 @@
 # Patch-in proper Karaf version into the startup script
 sed -i.bk "s/apache-karaf-\$KARAF_VERSION/$KARAF_DIR/g" bin/onos-service
 sed -i.bk "s/apache-karaf-\$KARAF_VERSION/$KARAF_DIR/g" bin/onos-client
-rm -f *.bk
+rm -f bin/*.bk
 mv bin/onos-client bin/onos
 chmod a+x bin/onos-service bin/onos