api-guide: fix the file injection considerations drift
api-guide: fix the file injection considerations drift

When these docs were initially imported [1] the "Considerations"
section was after "Server personality" but [2] refactored the
latter and forgot about the former. This fixes that so
"Considerations" is now just nested into the "Server personality"
section.

[1] I6d5ba6b96772e0f17fc7484312222110ec103bbf
[2] Ibbffdb00d1529a386f338da4776eb614891731c8

Change-Id: Ife6acefd42b9b2f5910fe8f0b1b001eeec80ff06

rahulunair/nova,openstack/nova,klmitch/nova,klmitch/nova,openstack/nova,mahak/nova,openstack/nova,mahak/nova,rahulunair/nova,klmitch/nova,rahulunair/nova,klmitch/nova,mahak/nova