mongo stuff to agent/mongod, add EnsureMongoServer

provider/local/prereqs_test.go

 // Copyright 2013 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
 package local
 
 import (
         "fmt"
         "io/ioutil"
         "os"
         "path/filepath"
@@ skipping 26 matching lines @@
         // found.
         lxclsPath = "/bin/true"
 }
 
 func (s *prereqsSuite) SetUpTest(c *gc.C) {
         s.LoggingSuite.SetUpTest(c)
         s.tmpdir = c.MkDir()
         s.testMongodPath = filepath.Join(s.tmpdir, "mongod")
         lxclsPath = filepath.Join(s.tmpdir, "lxc-ls")
         s.PatchEnvironment("PATH", s.tmpdir)
-
-        mongo.JujuMongodPath = "/somewhere/that/doesnt/exist"
+        s.PatchValue(&mongo.JujuMongodPath, c.MkDir())
 
         os.Setenv("JUJUTEST_LSB_RELEASE_ID", "Ubuntu")
         err := ioutil.WriteFile(filepath.Join(s.tmpdir, "lsb_release"), []byte(lsbrelease), 0777)
         c.Assert(err, gc.IsNil)
 }
 
 func (s *prereqsSuite) TearDownTest(c *gc.C) {
         s.testMongodPath = ""
         lxclsPath = "/bin/true"
         s.LoggingSuite.TearDownTest(c)
@@ skipping 103 matching lines @@
         os.Setenv("JUJUTEST_LSB_RELEASE_ID", "NotUbuntu")
         err = VerifyPrerequisites(instance.LXC)
         c.Assert(err, gc.ErrorMatches, "(.|\n)*Linux Containers \\(LXC\\) userspace tools must be installed(.|\n)*")
         c.Assert(err, gc.Not(gc.ErrorMatches), "(.|\n)*apt-get install(.|\n)*")
 
         err = ioutil.WriteFile(lxclsPath, nil, 0777)
         c.Assert(err, gc.IsNil)
         err = VerifyPrerequisites(instance.LXC)
         c.Assert(err, gc.IsNil)
 }