Catch exceptions from setLockCredential()

When LockPatternUtils#setLockCredential() fails, it can either return
false or throw an exception.  Catch the exception and treat it the same
way as a false return value, to prevent crashing com.android.settings.

Bug: 253043065
Test: Tried setting lockscreen credential while in secure FRP mode using
      smartlock setup activity launched by intent via adb.  Verified
      that com.android.settings no longer crashes due to the exception
      from LockPatternUtils#setLockCredential().
Change-Id: I48b9119c19fb6378b1f88d36433ee4f4c8501d76