Buggy 'CodeChecker parse --print-steps' filename outputs when a report is ranging across TUs.
**Describe the bug**
'CodeChecker parse --print-steps' prints incorrect filenames for some report steps when the report ranges across multiple translation units. Specifically, all the filenames are assumed to be the same as the first step's filename.

**CodeChecker version**
```
CodeChecker analyzer version:
---------------------------------------------------------------
Kind                 | Version
---------------------------------------------------------------
Base package version | 6.10.1
Package build date   | 2019-08-29T17:09
Git commit ID (hash) | 400ec527568fdfee5e4f02d1384d408bac2745b4
Git tag information  | 6.10.1
---------------------------------------------------------------
```

**Possible bug fix**
```
243                     for index, event in enumerate(events): 
244                         output.write(index_format % (index + 1))        
245                         source_file = report.files[event['location']['file']]    
246                         # patched (begin)                                                                     
247                         trimmed_source_file = \\    
248                             util.trim_path_prefixes(source_file,             
249                                                     self._trim_path_prefixes)   
250                         # patched (end)            
251                         output.write(       
252                             self.__format_bug_event(None,         
253                                                     None,         
254                                                     event,           
255                                                     trimmed_source_file))     
```            
Modifying `analyzer/codechecker_analyzer/cmd/parse.py` as above by adding Line 247~249 resolved the problem.

diff --git a/analyzer/codechecker_analyzer/cmd/parse.py b/analyzer/codechecker_analyzer/cmd/parse.py
index e31ca85d..21ce7822 100644
--- a/analyzer/codechecker_analyzer/cmd/parse.py
+++ b/analyzer/codechecker_analyzer/cmd/parse.py
@@ -243,6 +243,9 @@ class PlistToPlaintextFormatter(object):
                     for index, event in enumerate(events):
                         output.write(index_format % (index + 1))
                         source_file = report.files[event['location']['file']]
+                        trimmed_source_file = \\
+                            util.trim_path_prefixes(source_file,
+                                                    self._trim_path_prefixes)
                         output.write(
                             self.__format_bug_event(None,
                                                     None,
['analyzer/codechecker_analyzer/cmd/parse.py']