tests/fetch: Allow to work on python 2.6

Currently the fetch tests fail on python 2.6 since check_output
doesn't exist on this version of python. Use bb.process instead
to avoid this problem.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
test/fetch: Split the network tests from the rest of the fetcher tests

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
test/fetch: Allow the conditional network tests to work under python 2.6

The skipIf decorator is unavailable under python 2.6 and finding a syntax
works there is hard. This patch does allow network tests under 2.6.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
fetch2: Fix missing function call

Fix the issue:

File: '/srv/home/pokybuild/yocto-autobuilder-new/yocto-slave/build-appliance/build/bitbake/lib/bb/fetch2/__init__.py', lineno: 813, function: try_mirror_url
     0809:    except bb.fetch2.BBFetchException as e:
     0810:        if isinstance(e, ChecksumError):
     0811:            logger.warn("Mirror checksum failure for url %s (original url: %s)\nCleaning and trying again." % (newuri, origud.url))
     0812:            logger.warn(str(e))
 *** 0813:            self.rename_bad_checksum(ud, e.checksum)
     0814:        elif isinstance(e, NoChecksumError):
     0815:            raise
     0816:        else:
     0817:            logger.debug(1, "Mirror fetch failure for url %s (original url: %s)" % (newuri, origud.url))
Exception: NameError: global name 'self' is not defined

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
git: remove symling before updating mirror tarball

* with read-only PREMIRROR (e.g. mounted over NFS or CIFS
  and referenced as file:///mnt/premirror) we cannot use
  BB_GENERATE_MIRROR_TARBALLS because all git2_abc.git.tar.gz
  files later became just symlinks to read-only location in PREMIRROR
  (it works fine on first build and for new components, because
  at that time there isn't tarball on PREMIRROR yet).

  ERROR: Fetcher failure: Fetch command failed with exit code 141, output:
  tar (child): /build/downloads/git2_abc.git.tar.gz: Cannot open: Read-only file system
  tar (child): Error is not recoverable: exiting now

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>