MYNEWT-518 boot - Allow test+confirm as single act

Currently, to permanently run the alternate image, the boot loader
requires the following sequence:

1. image test <slot-01-hash>
2. reboot
3. image confirm

The new feature is to remove the need for the third step. The user
should be able to permanently switch images with this sequence:

1. image confirm <slot-01-hash>
2. reboot
diff --git a/boot/bootutil/test/src/boot_test.c b/boot/bootutil/test/src/boot_test.c
index a0e8069..98972f3 100644
--- a/boot/bootutil/test/src/boot_test.c
+++ b/boot/bootutil/test/src/boot_test.c
@@ -51,6 +51,8 @@
 TEST_CASE_DECL(boot_test_invalid_hash)
 TEST_CASE_DECL(boot_test_revert)
 TEST_CASE_DECL(boot_test_revert_continue)
+TEST_CASE_DECL(boot_test_permanent)
+TEST_CASE_DECL(boot_test_permanent_continue)
 
 TEST_SUITE(boot_test_main)
 {
@@ -71,6 +73,8 @@
     boot_test_invalid_hash();
     boot_test_revert();
     boot_test_revert_continue();
+    boot_test_permanent();
+    boot_test_permanent_continue();
 }
 
 int