Remove sometimes-unnecessary props read from svn_wc_get_prop_diffs().
Remove sometimes-unnecessary props read from svn_wc_get_prop_diffs().

Review by: philip

* subversion/libsvn_wc/props.c
  (svn_wc_get_prop_diffs): Rearrange, avoiding an unnecessary read of
    the WORKING properties file if the caller doesn't want to receive
    property changes.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@857275 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion