[erlang-server] minor bug fixes

Created by: sebastiw

dialyzer fixes for erlang-server

ping @tsloughter (2017/11) @jfacorro (2018/10) @robertoaloi (2018/10)

solves two dialyzer problems. First one is this issue #6354 and the corresponding dialyzer output

X_server.erl
Line 54 Column 66: The call X_server:store_key('env', NewEnv::[any()], Opts::#{'env':=#{'dispatch':=cowboy_router:dispatch_rules()}}) will never return since it differs in the 3rd argument from the success typing arguments: (any(), any(), [tuple()])

Line 57 Column 65: The call X_server:store_key(Key::any(), Value::any(), Opts::#{'env':=#{'dispatch':=cowboy_router:dispatch_rules()}}) will never return since it differs in the 3rd argument from the success typing arguments: (any(), any(), [tuple()])

Line 66 Column 1: Function store_key/3 has no local return

Line 67 Column 28: The call lists:keystore(Key::any(), 1, Opts::#{'env':=#{'dispatch':=cowboy_router:dispatch_rules()}}, {_,_}) will never return since the success typing is (any(), pos_integer(), maybe_improper_list(), tuple()) -> nonempty_maybe_improper_list() and the contract is (Key, N, TupleList1, NewTuple) -> TupleList2 when Key :: term(), N :: pos_integer(), TupleList1 :: [Tuple], TupleList2 :: [Tuple,...], NewTuple :: Tuple, Tuple :: tuple()

The second dialyzer problem is

X_default_logic_handler.erl
Line 8 Column 2: The return type {binary() | non_neg_integer(),#{binary()=>binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | [])},atom() | binary() | [any()] | number() | {{non_neg_integer(),1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12,1..255},{byte(),byte(),byte()}} | {'with_tail',_,binary()} | #{atom() | binary()=>_}} in the specification of handle_request/3 is not a subtype of {binary() | non_neg_integer(),#{binary()=>binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | [])},#{}}, which is the expected return type for the callback of X_logic_handler behaviour

It's coming from #{} in logic_handler.mustache but the from default_logic_handler.mustache it's jsx:json_term() https://github.com/OpenAPITools/openapi-generator/blob/77e1ca56cf329bfb22b05f853587263fd0ff6503/modules/openapi-generator/src/main/resources/erlang-server/default_logic_handler.mustache#L25

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