Update astrolabe to v0.5.1 (#475)

Signed-off-by: xinyanw409 <wxinyan@vmware.com>

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/spf13/cobra v1.1.3
 	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.7.0
-	github.com/vmware-tanzu/astrolabe v0.5.0
+	github.com/vmware-tanzu/astrolabe v0.5.1
 	github.com/vmware-tanzu/velero v1.5.1
 	github.com/vmware/govmomi v0.22.2-0.20200329013745-f2eef8fc745f
 	github.com/vmware/virtual-disks v0.0.4

go.sum

@@ -934,8 +934,8 @@ github.com/valyala/tcplisten v0.0.0-20161114210144-ceec8f93295a/go.mod h1:v3UYOV
 github.com/vektah/gqlparser v1.1.2/go.mod h1:1ycwN7Ij5njmMkPPAOaRFY4rET2Enx7IkVv3vaXspKw=
 github.com/vishvananda/netlink v1.0.0/go.mod h1:+SR5DhBJrl6ZM7CoCKvpw5BKroDKQ+PJqOg65H/2ktk=
 github.com/vishvananda/netns v0.0.0-20171111001504-be1fbeda1936/go.mod h1:ZjcWmFBXmLKZu9Nxj3WKYEafiSqer2rnvPr0en9UNpI=
-github.com/vmware-tanzu/astrolabe v0.5.0 h1:W40sqipaaiYtGVYH62lr9hPhw4IEtMQx18SkFttAnVE=
-github.com/vmware-tanzu/astrolabe v0.5.0/go.mod h1:DmNbTi+9kTDzmvpJyn91MrQUXzcgagY8mFPjLEOfUyI=
+github.com/vmware-tanzu/astrolabe v0.5.1 h1:kCN/ngp8fnH48E+mj5LC1tZ9PK41Yg7YBQKBhoBk8F8=
+github.com/vmware-tanzu/astrolabe v0.5.1/go.mod h1:M98fF2oO0xkSfymdaQmuD5jo1wZIjZvm+jUmz67osUA=
 github.com/vmware-tanzu/velero v1.5.1 h1:PMcPfrhv91AfO/NPIWJDVUEql+DUixPnTjg+LTV95yI=
 github.com/vmware-tanzu/velero v1.5.1/go.mod h1:SIyHunlEyLVeKjWR34rv0mLeNVsH5wiR/EmQuUEo1/k=
 github.com/vmware/govmomi v0.20.3/go.mod h1:URlwyTFZX72RmxtxuaFL2Uj3fD1JTvZdx59bHWk6aFU=