mesh: Virtual address memory leak
mesh: Virtual address memory leak

Fixes a memory leak when a virtual address subscription is added for a
model that either has this VA already, or the model has no more space
for subscription addresses.

this is port of 7e49153bb7139d2cc58e4d7734e2cc5a52905421

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble