Several tests are built around mocking procfs of Linux via a regular
file system and make use of grub2-editenv.  Exclude them.

Also exclude threading test as it wants to read EFI variables which
requires superuser privileges.

Index: tests/Makefile
--- tests/Makefile.orig
+++ tests/Makefile
@@ -3,12 +3,8 @@
 # Peter Jones, 2019-06-18 11:10
 #
 
-TESTS = test.dmpstore.export \
-	test.efivar.export \
-	test.grubenv.var \
-	test.bootorder.var \
+TESTS = test.bootorder.var \
 	test.conin.var \
-	test.efivar.threading \
 	test.parse.db \
 	test.esl.annotation \
 	test.esl.sha256.unsorted \