config: use proper unconfigured default values for use_lvmetad and use_lvmpolld settings

config: use proper unconfigured default values for use_lvmetad and use_lvmpolld settings

Default value for lvmetad and lvmpolld has hooks in configure script,
the "lvmconfig --type default --unconfigured" should display:

   use_lvmetad = @DEFAULT_USE_LVMETAD@
   use_lvmpolld = @DEFAULT_USE_LVMPOLLD@

Note that these settings are not of string type. Recent change (the
DM_CONFIG_VALUE_FMT_STRING_NO_QUOTES formatting flag) makes it
possible to recognize that the setting is not of string type and if
there's unconfigured value defined for it, the enclosing " " is
automatically removed on output.