MINOR: cfgparse-global: parse options to allow non std keywords in discovery mode

MINOR: cfgparse-global: parse options to allow non std keywords in discovery mode

'Program' section is considered as deprecated now, see the commit 581c8a27d98c
("MEDIUM: mworker: depreciate the 'program' section"). So, the 'program'
section parser emits a warning every time since this commit, if its section is
presented. This makes impossible to launch the process in zero-warning mode.

After master-worker refactoring only the master process parses the 'program'
section. So, at first, in order to be able to start in zero-warning mode, we
need to parse in master process option, which allows deprecated keywords. Thus,
let's set in this commit KWF_DISCOVERY flag to
cfg_parse_global_non_std_directives parser, which parses
'expose-deprecated-directives' and 'expose-deprecated-directives' options.