Add stress test for many invocations and fix memory leak

[mbrandenburger]

Add another stress test to detect memory leaks.

[mbrandenburger]

For some reason my test fails but did not fail the entire CI test ... 🤔

[mbrandenburger]

EDITED: I suspect the changes made in #637 causing the enclave crash (earlier). Running the test without a949ca9 seems to pass.

[mbrandenburger]

The stress test runs by default with 1000 invocations (defaultInvocationCount = 1000).
Via export STRESS_TEST_INVOCATION_COUNT=10000 you can set the invocation count when testing locally with larger numbers.

Example:

export STRESS_TEST_INVOCATION_COUNT=10000
cd $FPC_PATH/integration
make stress_test

This should run for a while. Note that the go test framework aborts when exceeding a test run with more than 10min.

[mbrandenburger]

EDITED: I suspect the changes made in #637 causing the enclave crash (earlier). Running the test without a949ca9 seems to pass.

As mentioned earlier, the changes in #637 introduced a memory leak when decoding the creator certificate. Additionally, some pb_release calls were missing. Note that also some pb_release calls where missing before #637, in particular those two:

    pb_release(fpc_CleartextChaincodeRequest_fields, &cleartext_cc_request);
    pb_release(fpc_KeyTransportMessage_fields, &key_transport_message);

[mbrandenburger]

This PR not contains a fix for the memory leaks that causes the FPC enclave to crash after many invocations. @bvavala please have a look. Once this PR is ready and merged, we can look into PR #640.

[mbrandenburger]

Just squashed fixups so this PR is ready for merge.

[bvavala]

lg - pending CI