e2e: Print gitsrv logs if it fails to start

[2opremio]

I am using this PR to figure out what's wrong with gitsrv in some e2e invocations (see #2672 (comment) )

[2opremio]

I can't reproduce the problem by re-running the test, so let's get this merged to get more information when it happens again.

[2opremio]

The sooner I speak ... It failed at https://circleci.com/gh/fluxcd/flux/9165 :

The problem is that gitsrv fails to initialize because it cannot resolve github.com :S

The logs output this error in a loop:

# curl: (6) Could not resolve host: github.com
# gzip: invalid magic
# tar: Child returned status 1
# tar: Error is not recoverable: exiting now
#   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
#                                  Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:--  0:00:04 --:--:--     0* Could not resolve host: github.com

Maybe a problem with Kind? I will try to upgrade it.

Anyways, let's merge this.