audiohal: Exit instead of crashing when HAL factory can't be obtained

Replace LOG_ALWAYS_FATAL with ALOGE + exit, so the process still
restarts, but without a crash. This avoids confusion in bug triaging
and also helps to eliminate noise in bug reports statistics.

Bug: 36424777
Change-Id: I623cbc6a5b0d3351f849810dd67708d421efd61a
Test: reproduced error condition, checked that audio server restarts