Update after a new review

...k/src/androidTest/java/org/matrix/olm/OlmAccountTest.java

...k/src/androidTest/java/org/matrix/olm/OlmSessionTest.java

...k/src/androidTest/java/org/matrix/olm/OlmUtilityTest.java

...dk/src/main/java/org/matrix/olm/CommonSerializeUtils.java

...bSdk/olm-sdk/src/main/java/org/matrix/olm/OlmAccount.java

...bSdk/olm-sdk/src/main/java/org/matrix/olm/OlmUtility.java

java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.cpp

...LibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.cpp

...ibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.cpp

java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.cpp

java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_utility.cpp