routing: move locking for ReportPaymentSuccess and ReportPaymentFailure
routing: move locking for ReportPaymentSuccess and ReportPaymentFailure

All of the other mission control exported functions acquire their locks
immediately, and do not lock in the subsequent unexported functions.
This commit moves the lock up for the report payment functions so that
mission control's config values are covered by this lock, in preparation
for allowing config to be updated at runtime. Moving this lock means
that we will hold the lock for the additional time it takes to store a
single result, AddResult, to the store.

aakselrod/lnd,aakselrod/lnd