Make the Dockerfile work again

As a result of #1225 every Linux binary needed was not allowed
to come from busybox. Which caused the Dockerfile in this repo
and the image @ dockerhub to fail.

This PR relaxes that so that busybox binaries which proved to
work can be used. A whitelist was defined.

testssl.sh

@@ -18486,11 +18486,13 @@ create_cmd_line_string() {
 
 check_base_requirements() {
      local binary=''
+     local whitelist=' hexdump grep awk sed '
 
-     for binary in 'hexdump' 'dd' 'grep' 'awk' 'tr' 'sed' 'date' 'cat' 'ps' 'kill' 'head' 'tail' 'dirname';  do
+     for binary in 'hexdump' 'dd' 'grep' 'awk' 'tr' 'sed' 'wc' 'date' 'cat' 'ps' 'kill' 'head' 'tail' 'dirname';  do
           if ! type -p "${binary}" &> /dev/null; then
                fatal "You need to install ${binary} for this program to work" $ERR_RESOURCE
           fi
+          [[ ${whitelist} =~ \ ${binary}\  ]] && continue
           "${binary}" --help 2>&1 | grep -iq busybox
           if [[ $? -eq 0 ]]; then
                fatal "${binary} is from busybox. Please install a regular binary" $ERR_RESOURCE