tests: Use get_bootloader_message_blk_device() to find /misc.

Since commit fb00d82f32 has added
get_bootloader_message_blk_device() as an API, switch the tests-local
implementation to it.

Test: recovery_component_test on angler.
Test: recovery_component_test on a local build that doesn't have /misc.
Change-Id: I4f5f542cb9ef58292c587a677da73d8822db7262

tests/component/uncrypt_test.cpp

@@ -30,8 +30,6 @@
 #include <bootloader_message/bootloader_message.h>
 #include <gtest/gtest.h>
 
-#include "common/component_test_util.h"
-
 using namespace std::string_literals;
 
 static const std::string UNCRYPT_SOCKET = "/dev/socket/uncrypt";
@@ -65,7 +63,8 @@ class UncryptTest : public ::testing::Test {
 
     ASSERT_TRUE(success) << "uncrypt service is not available.";
 
-    has_misc = parse_misc();
+    std::string err;
+    has_misc = !get_bootloader_message_blk_device(&err).empty();
   }
 
   void SetupOrClearBcb(bool isSetup, const std::string& message,