Went through a lot of questions, but nothing seems to be solving my issue. Or to be more precise I am not sure if I am doing the whole thing correctly. So here it is:
Ha
1) First make jenkins as real user by editing /etc/passwd file Change
/bin/false to /bin/bash
2) Login to jenkins user, Now Jenkins home directory will be /var/lib/jenkins
su - jenkins
3)Generate ssh keys again ( keys will be created in /var/lib/jenkins/.ssh)
ssh-keygen -t rsa
4) copy id_rsa.pub key and paste in your git's authorized_keys file
5) Still if it won't work, probably you have to check permissions of your .ssh directory and contents
chmod 700 ~/.ssh && chmod 600 ~/.ssh/*