Correct spelling mistake
Correct spelling mistake

spelling mistake in api/configurations.py at line 253.
The word "invalid" is misspelt.

Closes-Bug: #1585478
Change-Id: I84fbee9b947509108348ce312a148e0c49afbd28

zhangg/trove,openstack/trove,mmasaki/trove,hplustree/trove,mmasaki/trove,zhangg/trove,mmasaki/trove,hplustree/trove,openstack/trove