Recommended update for grub2

This recommended update for grub2 fixes the following issues:

- Fix wrong escape sequence in previous commit (boo#955115)
* modified grub2-snapper-plugin.sh

- Fix snapshot booting on s390x (boo#955115)
* modified grub2-snapper-plugin.sh

Fixed bugs
bnc#955115
[s390x] cannot boot into snapshot after online migration to sles12sp1
Selected Binaries
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