Fix shell for kill command

Base shell is not support -SIG notation, so directly
specify QUIT command.

Change-Id: I98aa7c96f59cb366eef4f012238cdc222305c1ef
diff --git a/src/com/mirantis/mcp/CCP.groovy b/src/com/mirantis/mcp/CCP.groovy
index 4f48fe1..b90d5d4 100644
--- a/src/com/mirantis/mcp/CCP.groovy
+++ b/src/com/mirantis/mcp/CCP.groovy
@@ -66,6 +66,6 @@
     def proxyPid = sh(script: "cat ${confDir}/nginx-${localPort}.pid",
                       returnStdout: true).trim()
     if ( proxyPid ) {
-        sh "kill -SIGQUIT ${proxyPid}"
+        sh "kill -QUIT ${proxyPid}"
     }
 }