mon: OSDMonitor: receive CephInt on 'osd pool set' instead on CephString

This partially reverts 2fe0d0d9 in order to allow Emperor monitors to
forward mon command messages to Dumpling monitors without breaking a
cluster.

The need for this patch became obvious after issue #6796 was triggered.
Basically, in a mixed cluster of Emperor/Dumpling monitors, if a client
happens to obtain the command descriptions from an Emperor monitor and
then issue an 'osd pool set' this can turn out in one of two ways:

1. client msg gets forwarded to an Emperor leader and everything's a-okay;
2. client msg gets forwarded to a Dumpling leader and the string fails to
be interpreted without the monitor noticing, thus leaving the monitor with
an uninitialized variable leading to trouble.

If 2 is triggered, a multitude of bad things can happen, such as thousands
of pg splits, due to a simple 'osd set pool foo pg_num 128' turning out
to be interpreted as 109120394 or some other random number.

This patch is such that we make sure the client sends an integer instead
of a string. We also make sure to interpret anything the client sends as
possibly being a string, or an integer.

Fixes: 6796
Backport: emperor

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
(cherry picked from commit 337195f04653eed8e8f153a5b074f3bd48408998)
mon: OSDMonitor: drop cmdval_get() for unused variable

We don't ever use any value as a float, so just drop obtaining it.  This
makes it easier to partially revert 2fe0d0d9 in an upcoming patch.

Backport: emperor

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
(cherry picked from commit 7191bb2b2485c7819ca7b9d9434d803d0c94db7a)
mon/OSDMonitor: take 'osd pool set ...' value as a string again

We ran into problems before when we made this a string because a mixed
cluster of mons might forward a client request with the wrong schema.
To make this work, we make the new code understand both the new and
old schema, and also backport a change to emperor and dumpling to
handle the new schema.

For the previous attempt to do this, see:
 337195f04653eed8e8f153a5b074f3bd48408998
 2fe0d0d97af95c22db80800f5b9da51f672d9407

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit 5c6dc94e18d83af2699e5872925be3335d49726e)