doc/cephadm: small improvements to operations.rst

doc/cephadm: small improvements to operations.rst

Remove "*" around CLI command placeholders that was rendered in literal strings.
Leave only the usual "<placeholder>" string.

Use title case consistently in section titles.
Add links to more information.
Move a label about logs to the right section.
Use double backticks consistently for literal strings.
Use confval role instead of literal inline for config keys in text.

Fix word capitalization and minor changes to words.
Use Monitor, Manager, etc. instead of MON, MGR, etc.
Improve markup. Improve prompt usage.
Fix duplicate text and remove an unnecessary section.

Delete spaces at end of lines. Add full stops or colons.

Signed-off-by: Ville Ojamo <14869000+bluikko@users.noreply.github.com>