Add cdma_3waycall_flash_delay key to CarrierConfig

Add KEY_CDMA_3WAYCALL_FLASH_DELAY_INT and default value to
CarrierConfigManager, and remove the references to the old config in
core/res/res/values/[config.xml/symbols.xml]
Merged-In: I53dc93defbfa7d1366e6ee066638d73df03f88d0

Bug: 29873049
Change-Id: I53dc93defbfa7d1366e6ee066638d73df03f88d0