email: add support for Server Name Indication (SNI)

Change the underlaying socket factory reference to SSLCertificateSocketFactory which
has support for SNI since 4.2, and remove the access to the obsolete methods from
the old factory reference.
This change will setup the socket with a proper hostname prior to the ssl handshake.

Change-Id: I494312721979a40a01699f5c15028dfafe7d07a9
JIRA: CYAN-3775
Issue: https://jira.cyanogenmod.org/browse/CYAN-3775
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>