container: avoid installing docs using the dnf configuration

container: avoid installing docs using the dnf configuration

Avoid installing docs by using the dnf configuration tsflags parameter,
passing the nodocs flag. This tells dnf and rpm not to install
documentation, such as manpages. Stop installing the docs just to delete
them later with an `rm -rf` type command.  Now the docs don't get
installed in the first place, saving space, but the rpm is happy
(`rpm -Va` no longer shows docs as 'missing').

Fixes: https://tracker.ceph.com/issues/69868
Signed-off-by: John Mulligan <jmulligan@redhat.com>