CBQE-930: rename membase_install* in install_server + optimizations

membase_install and membase_install_win is responsible for the installation couchbase and membase server, so the name is confusing

Change-Id: I04256d519db4c772a636bff913bd1d26d59bad50
Reviewed-on: http://review.couchbase.org/23542
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: buildbot <build@couchbase.com>