CBD-816 Basic UI support for recovery mode.

When cluster is in recovery mode, servers section will have
additional button to abort the recovery. Rebalance, fail over and
other similar buttons will be disabled.

Change-Id: I88db22066dade6a97b2acf38b10aa04d370cf7e9
Reviewed-on: http://review.couchbase.org/25242
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>