bug22191: Remove :wait-flush argument from solr-commit, solr-optimize.

The :wait-flush option to SOLR commit and optimize operations has
been deprecated and was removed in Solr 4.0, causing the solr client
to fail when interacting with newer servers.

Remove this keyword option.

Tests added for:     none
make test-suite run? lisp-prepush

releases notes: none needed, keyword not documented.

Change-Id: Ic1e692d83a53b4cb55efce12a542ea4f7ebd7268