PBAP: Strip unwanted braces and spaces from telephone number.

This patch removes unwanted spaces and braces from the telephone
number on vcard entry formation. Handsfree call was failing because
of these characters due to handling of only digits in utl_isdialstr
API in BD stack (external/bluetooth/bluedroid/bta/ag/bta_ag_cmd.c)

Change-Id: I2d63967059a9cb97f214b370fac17234f6e58f55