enb_ue not found during ContextSetupResponse handling. Possible race condition?

[spencersevilla]

I encountered a codepath once wherein the ogs_assert on enb_ue failed (see #3 ). Not sure why this happened, because the MME literally created this enb_ue ID in order to send the ContextSetupReequest, which MUST have been sent before the MME could have possibly handled a ContextSetupResponse.

I will dig further but in the meantime I suspect a race condition due to the lack of mutexes/locks on the enb_ue list.

[pathiratk]

I have added the lock for get and set functions