Give CPACK a pre-edited spec file.

twistd by default starts with umask 077.
This is why buildbot has umask setting.

rpm by default takes file and directory umask
from the build directory.

When building tarantool rpm under buildbot,
twistd default umask was inherited. Thus
all paths were created in rwx-- mode.

Now add to this cmake bug CMake bug 0012864.
That is, by default, cmake cpack generator
adds %dir directive for every intermediate
dir into the spec.

E.g. if there is a destination file /etc/rc.d/foo,
the spec gets
%dir /etc
%dir /etc/rc.d

Together with the default dir access mask of
twistd this nicely messed up our rpm install: an
install of Tarantool 1.4.8-59 rpm for CentOS would change
/etc and /usr access mode to 700.

Two things are done about that: Tarantool no longer
uses a cpack generated cpeck file. Extraneous %dir
directives are removed from the spec file. This
should minimize the damage of a broken twistd config,
should it happen again.

All buildslaves are reconfigured and restarted with umask 022.