graft::Context.set - OnExpired invoked much later than specified in 'ttl' parameter

[mbg033]

Example code:
https://github.com/graft-project/graft-ng/blob/develop-rta0719/graftlets/rta/requests/storepaymentdata.cpp#L107

SALE_TTL is defined as

const std::chrono::seconds SALE_TTL = std::chrono::seconds(60);

log:

2019-08-05 19:14:14.129 7fbcf3b2b700 DEBUG supernode.storepaymentdatarequest graftlets/rta/requests/storepaymentdata.cpp:111 storing payment data in global context: d2a6bba14e1

2019-08-05 19:19:29.331 7fbcf1b24700 DEBUG supernode.storepaymentdatarequest graftlets/rta/requests/storepaymentdata.cpp:108 on_expired: payment_id expired: d2a6bba14