esx: Fix build when libcurl debug is enabled

When building libvirt with libcurl debug enabled (with
ESX_VI__CURL__ENABLE_DEBUG_OUTPUT set), the message bellow pops up:

make[3]: Entering directory '/mnt/data/gitroot/libvirt/src'
CC esx/libvirt_driver_esx_la-esx_vi.lo
esx/esx_vi.c: In function 'esxVI_CURL_Debug':
esx/esx_vi.c:191:5: error: enumeration value 'CURLINFO_SSL_DATA_IN' not handled in switch [-Werror=switch-enum]
switch (type) {
^~~~~~
esx/esx_vi.c:191:5: error: enumeration value 'CURLINFO_SSL_DATA_OUT' not handled in switch [-Werror=switch-enum]
esx/esx_vi.c:191:5: error: enumeration value 'CURLINFO_END' not handled in switch [-Werror=switch-enum]

Our build requires at least libcurl 7.18.0, which is pretty stable since
it was release in 2008. Fix this problem by handling the mentioned enums
in the code.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>