Substring checking for SHA1 of kernel and local repo inverted

Invert the substirng checking: check if the SHA1 of the kernel is
contained in the SHA1 of the repo, since this last could be longer.

In order to do this, the following steps are followed:
- take the kernel release (uname -a), e.g.
  "4.4.88-g0e6b355-00003-g36e8d7f";
- take the last element, considering '-g' as separator, e.g. "36e8d7f";
- check if this SHA1 is contained in the SHA1 of the current repository.