More Backports for Stable 2.3.5 (#10430)

* revert some changes, could be buggy (#10399)

* ci: clean up gitlab-ci.yml leftovers from previous merge (#10429)

* 10000 > 5000 (#10422)

addresses #10418

* fix underflow in pip, closes #10419 (#10423)

* fix panic when logging directory does not exist, closes #10420 (#10424)

* Update hardcoded headers for Foundation, Ropsten, Kovan and Classic (#10417)

* update foundation to #7262209

* update kovan to #10434561

* update ropsten to #5027841

* update classic to #7555073

* Update Ropsten headers to #5101569

parity/cli/mod.rs

@@ -899,7 +899,7 @@ usage! {
 		["Snapshot Options"]
 			FLAG flag_no_periodic_snapshot: (bool) = false, or |c: &Config| c.snapshots.as_ref()?.disable_periodic.clone(),
 			"--no-periodic-snapshot",
-			"Disable automated snapshots which usually occur once every 10000 blocks.",
+			"Disable automated snapshots which usually occur once every 5000 blocks.",
 
 			ARG arg_snapshot_threads: (Option<usize>) = None, or |c: &Config| c.snapshots.as_ref()?.processing_threads,
 			"--snapshot-threads=[NUM]",