Use explicit .c_str() for hidl_string

hidl_string no longer will provide an implicit cast to const char* as it
interfers with other expected behaviors of the class.  It now emulated
std::string in requiring a call to .c_str() to get the same behavior.

Bug:  36532780
Test:  Build the tree
Change-Id: I265590c7c18f425e44863df062a56b67519a932a
diff --git a/automotive/evs/1.0/default/EvsEnumerator.cpp b/automotive/evs/1.0/default/EvsEnumerator.cpp
index 731e21b..b25d418 100644
--- a/automotive/evs/1.0/default/EvsEnumerator.cpp
+++ b/automotive/evs/1.0/default/EvsEnumerator.cpp
@@ -99,7 +99,7 @@
     }
 
     // Construct a camera instance for the caller
-    pActiveCamera = new EvsCamera(cameraId);
+    pActiveCamera = new EvsCamera(cameraId.c_str());
     pRecord->activeInstance = pActiveCamera;
     if (pActiveCamera == nullptr) {
         ALOGE("Failed to allocate new EvsCamera object for %s\n", cameraId.c_str());