Some minor improvements

* destroy/free/shutdown/close in reverse order of allocation
* more static/auto_Xfree
* less variables/strlen/GString
* properly `\0`-terminate string of testcase

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

tests/unittests/test_common.c

@@ -546,7 +546,7 @@ prof_occurrences_of_large_message_tests(void** state)
     char* haystack = malloc(haystack_sz);
     const char needle[] = "needle ";
     while (haystack_sz - haystack_cur > sizeof(needle)) {
-        memcpy(&haystack[haystack_cur], needle, sizeof(needle) - 1);
+        memcpy(&haystack[haystack_cur], needle, sizeof(needle));
         expected = g_slist_append(expected, GINT_TO_POINTER(haystack_cur));
         haystack_cur += sizeof(needle) - 1;
     }