configure.py: enable alloc failure injection for dev and debug modes
configure.py: enable alloc failure injection for dev and debug modes

We have numerous tests that rely on the seastar alloc failure injection
infrastructure to test the exception safety of different components.
These tests are essentially useless when the said infrastructure is
not enabled, which is currently the case for all build modes, allowing
bugs to sneak in undetected.
Enable the allocation failure injection infrastructure for the dev and
debug modes. Sanitize is excluded as it produces some (suspected false
positive) failures and is not run in gating either currently.

Tests: unit(dev, debug)

Signed-off-by: Botond Dénes <a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>
Message-Id: <20200117104747.748866-1-a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>

scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla