install-deps.sh: remove existing ceph-libboost of different version

install-deps.sh: remove existing ceph-libboost of different version

we install different versions of precompiled ceph-libboost packages
for different branches when building and testing them on ubuntu test
nodes. for instance,

- nautilus, octopus: v1.72
- pacific: v1.73

they share the same set of test nodes. and these ceph-libboost packages
conflict with each other, because they install files to the same places.

in order to avoid the confliction, we should uninstall existing packages
before installing a different version of ceph-libboost packages.

ceph-libboost${version}-dev is a package providing the shared headers of
boost library, so, in this change we check if it is installed before
returning or removing the existing packages.

Signed-off-by: Kefu Chai <kchai@redhat.com>
(cherry picked from commit 939b147a55192c21e98d21cb380d0ec0b2ca84d5)

Conflicts:
	install-deps.sh: trivial resolution