shall not initialize from an empty shared_ptr
avoid thread sanitizer warning in the test of AcknowledgementTest.BEH_CallOnce
avoid thread sanitizer warning in the test of AcknowledgementTest.BEH_CallRemove
notify shall be protected under mutex
Merge branch 'account_transfer' into MAID-524_sanitizer_analysis_account_transfer
Revert "notify shall be protected under mutex"

This reverts commit a3da3713d4782e44e740a35c5178edbe92e2d59e.
taking off const, as pass-by-value now
Merge pull request #77 from maqi/MAID-524_sanitizer_analysis_account_transfer

MAID-524_sanitizer_analysis_account_transfer