revert: Bollard update rolled back, closes #66

Using Bollard 0.19.x meant that network stats weren't being recorded correctly. Updated local unhealthy container to use a speed test in order to check for network IO.

Cargo.lock

@@ -129,9 +129,9 @@ checksum = "1b8e56985ec62d17e9c1001dc89c88ecd7dc08e47eba5ec7c29c7b5eeecde967"
 
 [[package]]
 name = "bollard"
-version = "0.19.1"
+version = "0.18.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "899ca34eb6924d6ec2a77c6f7f5c7339e60fd68235eaf91edd5a15f12958bb06"
+checksum = "97ccca1260af6a459d75994ad5acc1651bcabcbdbc41467cc9786519ab854c30"
 dependencies = [
  "base64",
  "bollard-stubs",
@@ -162,12 +162,11 @@ dependencies = [
 
 [[package]]
 name = "bollard-stubs"
-version = "1.48.3-rc.28.0.4"
+version = "1.47.1-rc.27.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "64ea257e555d16a2c01e5593f40b73865cdf12efbceda33c6d14a2d8d1490368"
+checksum = "3f179cfbddb6e77a5472703d4b30436bff32929c0aa8a9008ecf23d1d3cdd0da"
 dependencies = [
  "serde",
- "serde_json",
  "serde_repr",
  "serde_with",
 ]