test/test_rgw_crypto: free allocated test_in

test/test_rgw_crypto: free allocated test_in

When sanitizer is enabled, unittest__rgw_crypto shows

```
=================================================================
==136464==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 75023 byte(s) in 22 object(s) allocated from:
    #0 0xaaaabf7fb86c in operator new[](unsigned long) (/root/ceph/build/bin/unittest_rgw_crypto+0x48b86c) (BuildId: 8023dc30820215da92d6d4883620bedd8ac1190d)
    #1 0xaaaabf81db48 in TestRGWCrypto_verify_Encrypt_Decrypt_Test::TestBody() /root/ceph/src/test/rgw/test_rgw_crypto.cc:780:24
    #2 0xaaaabf9018ac in void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2605:10
    #3 0xaaaabf8b08a4 in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2641:14
    #4 0xaaaabf861f88 in testing::Test::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:2680:5
    #5 0xaaaabf863ecc in testing::TestInfo::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:2858:11
    #6 0xaaaabf8654cc in testing::TestSuite::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:3012:28
    #7 0xaaaabf881290 in testing::internal::UnitTestImpl::RunAllTests() /root/ceph/src/googletest/googletest/src/gtest.cc:5723:44
    #8 0xaaaabf90b7ac in bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2605:10
    #9 0xaaaabf8b7ac0 in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2641:14
    #10 0xaaaabf880708 in testing::UnitTest::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:5306:10
    #11 0xaaaabf823d70 in RUN_ALL_TESTS() /root/ceph/src/googletest/googletest/include/gtest/gtest.h:2486:46
    #12 0xaaaabf81f390 in main /root/ceph/src/test/rgw/test_rgw_crypto.cc:822:10
    #13 0xffff878673f8 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #14 0xffff878674c8 in __libc_start_main csu/../csu/libc-start.c:392:3
    #15 0xaaaabf74d62c in _start (/root/ceph/build/bin/unittest_rgw_crypto+0x3dd62c) (BuildId: 8023dc30820215da92d6d4883620bedd8ac1190d)

SUMMARY: AddressSanitizer: 75023 byte(s) leaked in 22 allocation(s).
```

test_in should be freed to address the warning.

Signed-off-by: Rongqi Sun <sunrongqi@huawei.com>