tests: Fix bugs related to gem5 Vision

This patch fixes refs under tests/pyunit/stdlib/resources.

Removes instances of {url_base} in refs.

Also, renames two refs: mongo_mock and mongo_dup_mock
to mongo-mock and mongo-dup-mock to follow naming
convention of other refs.

Change-Id: If115114bc7a89764e7c546b77a93d36d6a3b5f8a
Co-authored-by: Parth Shah <helloparthshah@gmail.com>
Co-authored-by: Harshil2107 <harshilp2107@gmail.com>
Co-authored-by: aarsli <arsli@ucdavis.edu>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/71360
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>

tests/pyunit/stdlib/resources/refs/workload-checks-custom-workload.json

@@ -6,7 +6,7 @@
         "architecture": "X86",
         "is_zipped": false,
         "md5sum": "dbf120338b37153e3334603970cebd8c",
-        "url": "{url_base}/test-progs/hello/bin/x86/linux/hello64-static",
+        "url": "http://dist.gem5.org/dist/develop/test-progs/hello/bin/x86/linux/hello64-static",
         "source": "src/simple",
         "resource_version": "1.0.0",
         "gem5_versions": [

tests/pyunit/stdlib/resources/refs/workload-checks.json

@@ -6,7 +6,7 @@
         "architecture": "X86",
         "is_zipped": false,
         "md5sum": "4838c99b77d33c8307b939c16624e4ac",
-        "url": "{url_base}/kernels/x86/static/vmlinux-5.2.3",
+        "url": "http://dist.gem5.org/dist/develop/kernels/x86/static/vmlinux-5.2.3",
         "source": "src/linux-kernel",
         "resource_version": "1.0.0",
         "gem5_versions": [
@@ -20,7 +20,7 @@
         "architecture": "X86",
         "is_zipped": true,
         "md5sum": "90e363abf0ddf22eefa2c7c5c9391c49",
-        "url": "{url_base}/images/x86/ubuntu-18-04/x86-ubuntu.img.gz",
+        "url": "http://dist.gem5.org/dist/develop/images/x86/ubuntu-18-04/x86-ubuntu.img.gz",
         "source": "src/x86-ubuntu",
         "root_partition": "1",
         "resource_version": "1.0.0",