Tweak GroupAntiAffinityFilter doc

fixes bug 1128587

Gary Kotton noted in the bug that multiple hints were being
specified in the commandline example for the GroupAntiAffinityFilter

This patch fixes this and adds a descriptive line about what the hint
is used for.

patch2 encloses group and server1 in the description in literal tags

patch3 fixes one of the literal tags

Change-Id: Ie15ea3deebd44e0caaf5a01d45cb90d5ed0a9d9e
Merge "Tweak GroupAntiAffinityFilter doc"