Add Tequilapi client timeout

[tcharding]

As described in issue #386 current tequilapi client does not use a timeout. In current go version (1.11) stdlib http.Client does implement timeout functionality (also available in 1.9 and 1.10).

From /usr/lib/go/src/net/http/client.go (golang version 1.11.1):

// A Client is an HTTP client. Its zero value (DefaultClient) is a
// usable client that uses DefaultTransport.
...
type Client struct {
...
// Timeout specifies a time limit for requests made by this
// Client. The timeout includes connection time, any
// redirects, and reading the response body. The timer remains
// running after Get, Head, Post, or Do return and will
// interrupt reading of the Response.Body.
//
// A Timeout of zero means no timeout.
//
// The Client cancels requests to the underlying Transport
// as if the Request's Context ended.
//
// For compatibility, the Client will also use the deprecated
// CancelRequest method on Transport if found. New
// RoundTripper implementations should use the Request's Context
// for cancelation instead of implementing CancelRequest.
Timeout time.Duration

We can use this to add a timeout to the tequilapi client.

First do a couple of clean up patches in tequilapi/client, with this PR applied tequilapi/client/*.go lint cleanly. Use capital letters for acronyms as is standard Golang convention. Then add timeout of 120 seconds to the tequilapi client.

Tested by setting timeout to 1 nanosecond and running client

build/myst/myst cli                                                                                                                           ✱ (git:tequilapi-timeout)
2018-10-18T05:02:55.358443336 [Info] Starting Mysterium Node (source.dev-build)
2018-10-18T05:02:55.361336074 [Info] [Openvpn check] OpenVPN 2.4.4 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Sep  5 2018
2018-10-18T05:02:55.361379991 [Info] [Openvpn check] library versions: OpenSSL 1.1.0g  2 Nov 2017, LZO 2.08
2018-10-18T05:02:55.36139322 [Info] [Openvpn check] Originally developed by James Yonan
2018-10-18T05:02:55.361395925 [Info] [Openvpn check] Copyright (C) 2002-2017 OpenVPN Technologies, Inc. <sales@openvpn.net>
2018-10-18T05:02:55.361401316 [Info] [Openvpn check] Compile time defines: enable_async_push=no enable_comp_stub=no enable_crypto=yes enable_crypto_ofb_cfb=yes enable_debug=yes enable_def_auth=yes enable_dependency_tracking=no enable_dlopen=unknown enable_dlopen_self=unknown enable_dlopen_self_static=unknown enable_fast_install=needless enable_fragment=yes enable_iproute2=yes enable_libtool_lock=yes enable_lz4=yes enable_lzo=yes enable_maintainer_mode=no enable_management=yes enable_multihome=yes enable_pam_dlopen=no enable_pedantic=no enable_pf=yes enable_pkcs11=yes enable_plugin_auth_pam=yes enable_plugin_down_root=yes enable_plugins=yes enable_port_share=yes enable_selinux=no enable_server=yes enable_shared=yes enable_shared_with_static_runtimes=no enable_silent_rules=no enable_small=no enable_static=yes enable_strict=no enable_strict_options=no enable_systemd=yes enable_werror=no enable_win32_dll=yes enable_x509_alt_username=yes with_aix_soname=aix with_crypto_library=openssl with_gnu_ld=yes with_mem_check=no with_sysroot=no
2018-10-18T05:02:55.361412963 [Info] Using Eth endpoint: https://ropsten.infura.io
2018-10-18T05:02:55.361433519 [Info] Using Eth contract at address: 0xbe5F9CCea12Df756bF4a5Baf4c29A10c3ee7C83B
timeout

Closes: #386

Signed-off-by: Tobin C. Harding me@tobin.cc

[soffokl]

Looks good to me, but CI build should pass.

[tcharding]

I don't know what happened on this branch with all the merges of master. I rebased the original three patches on top of tip of master and used @soffokl's suggestion to fix my code fail (120 * time.Seconds). This means you lost the commit attribution though @soffokl :(

[soffokl]

Don't worry about applying my suggestion via Github. )

[Waldz]

LGTM