In call_ctx_free, all the resources associated with the CallCtx
were freed, but not the struct itself, which also was dynamically
allocated.

Direct leak of 24 byte(s) in 1 object(s) allocated from:
    #0 0x7f3b56061a50 in __interceptor_calloc (/lib64/libasan.so.5+0xefa50)
    #1 0x7f3b55ea6ffd in g_malloc0 (/lib64/libglib-2.0.so.0+0x53ffd)
    #2 0x409a95 in test_exported_props ../tests/test-exported.c:806
    #3 0x7f3b55ec91a9  (/lib64/libglib-2.0.so.0+0x761a9)