Currently, for usdt, the commands where both a pid and a binary path
are specified are not well supported. For example,
```
funccount -p <pid> 'u:<binary_path>:probe'
```
will count `probe` occurances for all binary paths in `pid`, not just
`<binary_path>`. The command
```
argdist -p <pid> 'u:<binary_path>:probe():s64:arg1'
```
will also count `probe` occurances for all binary paths in `pid`
with my previous patch.

Furthermore, suppose user want to trace linker `setjmp` probe point
with command
```
trace.py -p <pid> 'u:/usr/lib64/ld-2.17.so:setjmp'
```
Without my previous patch, user will have incorrect results as both
`libc:setjmp` and `rtld:setjmp` exists and the bcc just picks the first
one which is `libc:setjmp`. My last patch will cause `enable_probe`
failures if in the same usdt context, two probes have the same
probe_name but different provider name.

To fix all these issues, this patch passes additional binary path
to the pid-based usdt context, so that only probes from that particular
binary will be added to the context. This solved all the above
mentioned issues.
Signed-off-by: Yonghong Song <yhs@fb.com>