DOCS-875  operator
Update source/release-notes/2.4-upgrade.txt

Added section about forcing the upgradeLock and retrying for local mongos crashes during upgrade.
DOCS-1025 removing comment block from 2.4 doc
DOCS-924: removing comment blocks from 2.4 feature
DOCS-1174: correction to kerb environment varriable
merge+edits: DOCS-875
DOCS-1025 clarification about usePowerOf2Sizes and capped collections
changes to release notes to address SERVER-8710 and DOCS-1145
Updates with the correct module name for import

Signed-off-by: Sam Kleinman <samk@10gen.com>