Fix showing number repeat in call log for 4G conference call

If the numbers all are not existing in Contact, the empty contact
return as query result, but it is static object so that impacts
next queried result.

Need new a contact object to avoid modifying empty contact when
the contact is not present.

Change-Id: I914a6d5b053e4dd9cd193701b571522fb8bf523a
CRs-Fixed: 1085422