chore(package): update xen-api to 0.15.0

Fibonacci backoff on XenAPI calls.

package.json

@@ -108,7 +108,7 @@
     "tmp": "^0.0.33",
     "uuid": "^3.0.1",
     "ws": "^3.2.0",
-    "xen-api": "^0.14.2",
+    "xen-api": "^0.15.0",
     "xml2js": "^0.4.19",
     "xo-acl-resolver": "^0.2.3",
     "xo-collection": "^0.4.1",

yarn.lock

@@ -3938,6 +3938,10 @@ istanbul-reports@^1.1.3:
   dependencies:
     handlebars "^4.0.3"
 
+iterable-backoff@^0.0.0:
+  version "0.0.0"
+  resolved "https://registry.yarnpkg.com/iterable-backoff/-/iterable-backoff-0.0.0.tgz#e49660be7e1727fc52ee5c86c67cc3a427b4e109"
+
 jest-changed-files@^21.2.0:
   version "21.2.0"
   resolved "https://registry.yarnpkg.com/jest-changed-files/-/jest-changed-files-21.2.0.tgz#5dbeecad42f5d88b482334902ce1cba6d9798d29"
@@ -7336,9 +7340,9 @@ xdg-basedir@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/xdg-basedir/-/xdg-basedir-3.0.0.tgz#496b2cc109eca8dbacfe2dc72b603c17c5870ad4"
 
-xen-api@^0.14.2:
-  version "0.14.3"
-  resolved "https://registry.yarnpkg.com/xen-api/-/xen-api-0.14.3.tgz#09f688c54a8311f384bd034bb364293415bd7588"
+xen-api@^0.15.0:
+  version "0.15.0"
+  resolved "https://registry.yarnpkg.com/xen-api/-/xen-api-0.15.0.tgz#dc2d60dabadcaa156f568e118282cc094ceb3094"
   dependencies:
     babel-polyfill "^6.23.0"
     blocked "^1.2.1"
@@ -7346,6 +7350,7 @@ xen-api@^0.14.2:
     event-to-promise "^0.8.0"
     exec-promise "^0.7.0"
     http-request-plus "^0.4.0"
+    iterable-backoff "^0.0.0"
     json-rpc-protocol "^0.11.2"
     kindof "^2.0.0"
     lodash "^4.17.4"