Move plugin_push_current() before svn_binary() in svn_call()

Move the call to plugin_push_current() to be before the first call
to svn_binary() to ensure that svn_binary()'s calls to
plugin_config_get() retrieve the options from SourceSVN's config
options rather than any plugin inheriting from SourceSVN

Fixes #242

Backported from c88f88c

Author: bright-tools

SourceSVN/SourceSVN.php

@@ -315,10 +315,10 @@ private function svn_call( $p_repo=null ) {
 
 		# Get a full binary call, including configured parameters
 		if ( is_null( $s_call ) ) {
-			$s_call = self::svn_binary() . ' --non-interactive';
-
 			plugin_push_current( 'SourceSVN' );
 
+			$s_call = self::svn_binary() . ' --non-interactive';
+
 			if ( plugin_config_get( 'svnssl', false ) ) {
 				$s_call .= ' --trust-server-cert';
 			}