Bug 9612: Zconn parameters and elementSetName in _new_Zconn

Bug 9612: Zconn parameters and elementSetName in _new_Zconn

This patch makes a few adjustments in C4::Context::Zconn.
It does no longer pass the (ignored) auth, syntax parameters to _new_Zconn.
Note that auth was not completely ignored in theory, but we never pass
auth=1 [while not having user/password in koha-conf].

Furthermore, it removes the elementSetName for dom indexing. Using marcxml
here does not make a difference. It only adds a constraint on what is in
the dom-config files. (It could probably be removed there now..)

Two cosmetic code changes:
Removes unused label retry.
And moved 'servername' into the database name option.

Test plan:
When using Zebra with dom indexing, do a biblio and authority search.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>