add APACHE_HTTPD_CONF

https://github.com/Neilpang/acme.sh/issues/363

acme.sh

@@ -1808,6 +1808,11 @@ _apachePath() {
     return 1
   fi
   
+  if [ "$APACHE_HTTPD_CONF" ] ; then
+    _saveaccountconf APACHE_HTTPD_CONF "$APACHE_HTTPD_CONF"
+    httpdconf="$APACHE_HTTPD_CONF"
+    httpdconfname="$(basename $httpdconfname)"
+  else
     httpdconfname="$($_APACHECTL -V | grep SERVER_CONFIG_FILE= | cut -d = -f 2 | tr -d '"' )"
     _debug httpdconfname "$httpdconfname"
     
@@ -1825,6 +1830,7 @@ _apachePath() {
       httpdconf="$httpdroot/$httpdconfname"
       httpdconfname="$(basename $httpdconfname)"
     fi
+  fi
   _debug httpdconf "$httpdconf"
   _debug httpdconfname "$httpdconfname"
   if [ ! -f "$httpdconf" ] ; then