Fix a thinko in how the RemoteiOS Platform looked up files in the SDK & other
platform locations.  We didn't always do an exhaustive search through all the 
platform locations, so we would have to read some files out of memory even though
they existed in the exploded shared cache or SDK.

<rdar://problem/18385947>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@218157 91177308-0d34-0410-b5e6-96231b3b80d8