[SSHD-361][SSHD-362][SSHD-363] Upgrade to mina 2.0.8, bouncycastle 1.51 and jgit 3.4.1
[SSHD-361][SSHD-362][SSHD-363] Upgrade to mina 2.0.8, bouncycastle 1.51 and jgit 3.4.1

landro/mina-sshd,apache/mina-sshd,apache/mina-sshd,ieure/mina-sshd,landro/mina-sshd,lgoldstein/mina-sshd,avthart/mina-sshd,apache/mina-sshd,avthart/mina-sshd,lgoldstein/mina-sshd,ieure/mina-sshd,avthart/mina-sshd,ieure/mina-sshd,lgoldstein/mina-sshd,apache/mina-sshd,landro/mina-sshd,lgoldstein/mina-sshd