Add support for git clone issues

[tpgxyz]

Sometimes git clone fails:

24.11.2016 11:39:22Found api base url: https://abf.openmandriva.org/api/v1
24.11.2016 11:39:22Found build token: seJggzfVqeseXvTwmV9D
24.11.2016 11:39:22Found supported arches: x86_64,i586,armv7hl
24.11.2016 11:39:22Found native arches: x86_64,i586
24.11.2016 11:39:22Found supported platforms: openmandriva2014.0,cooker,3.0
24.11.2016 11:39:22Cloning into 'mdv'...
24.11.2016 11:39:32fatal: unable to access 'https://github.com/OpenMandrivaSoftware/docker-builder.git/': Couldn't resolve host 'github.com'
24.11.2016 11:40:52Config parsed successfuly.

Would be nice to add support for repeating to succesfully clone repo.

[fedya]

How to reproduce?

builder-c it's just a daemon for abf and this stuff working via system resolv.

probably it is tanmad host, right?

[tpgxyz]

@fedya this is lax server. I had to set up DNS in rancher for lax services to make it work.

[tpgxyz]

Here is some new development in this situation:
In function "int load_scripts " a check is needed for non-zero exit status from "git clone", and a retry till success.

builder-c/main.c

Line 298 in 2928ed3

int load_scripts(const char *git_repo, const char *git_branch, const char *platform_type) {