Fixes 3d87c6f - Invalid syntax for curl --time-cond

According to Curl man page, syntax for --time-cond attribute
should be "--time-cond file <path>", not "--time-cond <path>".

This can cause issues with outdated vmlinuz and initrd.im files,
once the files are downloaded, they are never replaced with never versions.

[0] https://curl.se/docs/manpage.html

lib/proxy/http_download.rb

@@ -26,7 +26,7 @@ def initialize(src, dst, connect_timeout: DEFAULT_CONNECT_TIMEOUT, verify_server
       # keep last changed file attribute
       args << "--remote-time"
       # only download newer files
-      args += ["--time-cond", dst.to_s]
+      args += ["--time-cond", "file", dst.to_s]
       # print stats in the end
       args += [
         "--write-out",

test/http_download_test.rb

@@ -17,7 +17,7 @@ def test_regular_call
       "--retry-delay", "10",
       "--max-time", "3600",
       "--remote-time",
-      "--time-cond", "dst",
+      "--time-cond", "file", "dst",
       "--write-out", "Task done, result: %{http_code}, size downloaded: %{size_download}b, speed: %{speed_download}b/s, time: %{time_total}ms",
       "--output", "dst",
       "--location", "src"
@@ -34,7 +34,7 @@ def test_regular_call_with_ssl_verify
       "--retry-delay", "10",
       "--max-time", "3600",
       "--remote-time",
-      "--time-cond", "dst",
+      "--time-cond", "file", "dst",
       "--write-out", "Task done, result: %{http_code}, size downloaded: %{size_download}b, speed: %{speed_download}b/s, time: %{time_total}ms",
       "--output", "dst",
       "--location", "src"