Add -json flag to mirror list|show

Signed-off-by: Joshua Colson <joshua.colson@gmail.com>

system/t04_mirror/ShowMirror5Test_gold

@@ -0,0 +1,46 @@
+{
+  "UUID": "82ca6517-ab0b-4be9-81bd-e884a07167f2",
+  "Name": "mirror1",
+  "ArchiveRoot": "http://cdn-fastly.deb.debian.org/debian/",
+  "Distribution": "stretch",
+  "Components": [
+    "main",
+    "contrib",
+    "non-free"
+  ],
+  "Architectures": [
+    "amd64",
+    "arm64",
+    "armel",
+    "armhf",
+    "i386",
+    "mips",
+    "mips64el",
+    "mipsel",
+    "ppc64el",
+    "s390x"
+  ],
+  "Meta": {
+    "Acquire-By-Hash": "yes",
+    "Architectures": "amd64 arm64 armel armhf i386 mips mips64el mipsel ppc64el s390x",
+    "Changelogs": "http://metadata.ftp-master.debian.org/changelogs/@CHANGEPATH@_changelog",
+    "Codename": "stretch",
+    "Components": "main contrib non-free",
+    "Date": "Sat, 14 Aug 2021 07:42:00 UTC",
+    "Description": " Debian 9.13 Released 18 July 2020\n",
+    "Label": "Debian",
+    "Origin": "Debian",
+    "Suite": "oldoldstable",
+    "Version": "9.13"
+  },
+  "LastDownloadDate": "0001-01-01T00:00:00Z",
+  "Filter": "",
+  "Status": 0,
+  "WorkerPID": 0,
+  "FilterWithDeps": false,
+  "SkipComponentCheck": false,
+  "SkipArchitectureCheck": false,
+  "DownloadSources": false,
+  "DownloadUdebs": false,
+  "DownloadInstaller": false
+}