Reclaim consults the _regions vector, so we don't want it moving around while
allocating more capacity. For that we take the reclaim lock. However, that
can cause a false-positive OOM during startup:
1. all memory is allocated to LSA as part of priming (2baa16b371)
2. the _regions vector is resized from 64k to 128k, requiring a segment
to be freed (plenty are free)
3. but reclaiming_lock is taken, so we cannot reclaim anything.
To fix, resize the _regions vector outside the lock.
Fixes#6003.
Message-Id: <20200311091217.1112081-1-avi@scylladb.com>
(cherry picked from commit c020b4e5e2)
cbbb15af5c