debian/: use ceph-osd for packaging crimson-osd

debian/: use ceph-osd for packaging crimson-osd

* debian/: remove ceph-crimson-osd package.
* debian/control: set `CEPH_OSD_BASENAME` env variable, which
  will be consumed by `ceph-osd.install`. alternatively, we could
  rename crimson-osd to ceph-osd in `override_dh_auto_install`,
  but let's go with this way at this moment, unless `mv` in
  `override_dh_auto_install` is proved to be better.
* ceph-osd.install: replace ceph-osd with crimson-osd if
  `CEPH_EXTRA_CMAKE_ARGS` has `WITH_SEASTAR` in it. this only
  happens when we are packaging the "crimson" flavor packages from
  jenkins.
* ceph-osd.install: `chmod +x` this file, as we need to use
  `/usr/bin/dh-exec` as the interpreter of it to perform variable
  substitution and install.

Signed-off-by: Kefu Chai <kchai@redhat.com>