Fix parsing git-like url

Change-Id: I864a088eb554da25cee6a77de82d70e5a4df3afa
diff --git a/src/com/mirantis/mk/Ssh.groovy b/src/com/mirantis/mk/Ssh.groovy
index 5fa3786..0f6c47f 100644
--- a/src/com/mirantis/mk/Ssh.groovy
+++ b/src/com/mirantis/mk/Ssh.groovy
@@ -19,7 +19,7 @@
 @NonCPS
 def getKnownHost(url){
      // test for git@github.com:organization/repository like URLs
-    def p = ~/.+@(.+\..+)\:{1}.*/
+    def p = ~/[a-z0-9\._\-]+@(.+\..+)\:{1}.*/
     def result = p.matcher(url)
     def host = ""
     if (result.matches()) {