Kill nginx process with SIGQUIT

By default kill sends SIGTERM which doesn't propertly handled
port release if such opened. Instead of that SIGQUIT correctly
closes process and releases opened by this propess ports.

Change-Id: I0c513c26315ffc53303b2ea79a166d7bdf6587be
diff --git a/src/com/mirantis/mcp/CCP.groovy b/src/com/mirantis/mcp/CCP.groovy
index 4f59edc..4f48fe1 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 ${proxyPid}"
+        sh "kill -SIGQUIT ${proxyPid}"
     }
 }