A bug has been discovered while trying to ALTER tablets KS and
specifying only 1 out of 2 DCs - the not specified DC's RF has been
zeroed. This is because ALTER tablets KS updated the KS only with the
RF-per-DC mapping specified in the ALTER tablets KS statement, so if a
DC was ommitted, it was assigned a value of RF=0.
This commit fixes that plus additionally passes all the KS options, not
only the replication options, to the topology coordinator, where the KS
update is performed.
`initial_tablets` is a special case, which requires a special handling
in the source code, as we cannot simply update old initial_tablet's
settings with the new ones, because if only ` and TABLETS = {'enabled':
true}` is specified in the ALTER tablets KS statement, we should not zero the `initial_tablets`, but
rather keep the old value - this is tested by the
`test_alter_preserves_tablets_if_initial_tablets_skipped` testcase.
Other than that, the above mentioned testcase started to fail with
these changes, and it appeared to be an issue with the test not waiting
until ALTER is completed, and thus reading the old value, hence the
test's body has been modified to wait for ALTER to complete before
performing validation.
(cherry picked from commit 2aabe7f09c)
1f6befe16d