ftrace tests: Use gdb_load_shlib result to lookup IPA in info sharedlibrary

ftrace tests: Use gdb_load_shlib result to lookup IPA in info sharedlibrary

Some fast tracepoints tests make sure that the in-process agent library
is properly loaded, by searching for the library name in "info
sharedlibrary".

Originally, it would search for the full path.  Since patch "Make ftrace
tests work with remote targets" [1], the "runtime" location of the IPA,
in the standard output directory, is not the same as the original
location, in the gdbserver build directory.  Therefore, the patch
changed the checks:

  gdb_test "info sharedlibrary" ".*${libipa}.*" "IPA loaded"

to

  gdb_test "info sharedlibrary" ".*[file tail ${libipa}].*" "IPA loaded"

so that only the "libinproctrace.so" part would be searched for.
Antoine (in CC) pointed out that I missed some, so I have to update
them.  In the mean time, I noticed that I missed a few test failures:
adding the SONAME to the IPA makes it possible for the test executable
to erroneously pick up libinproctrace.so from /usr/lib if the test
harness failed to put the libinproctrace.so we want to test in the right
place.  To mitigate that kind of error in the future, we can use the
return value of gdb_load_shlib (the path of the "runtime" version of the
library) and use that to search in the output of info sharedlibrary.

When testing locally, gdb_load_shlib returns the full normalized path of
the destination library, which the test executable should use e.g.:

  /path/to/gdb/testsuite/outputs/gdb.trace/thetest/libinproctrace.so

My testing showed that it was the same path that gdb displayed in info
sharedlibrary.  If the test executable picks up another
libinproctrace.so, the test will fail.

When testing remotely, gdb_load_shlib/gdb_remote_download only returns
us "libinproctrace.so", so the situation doesn't really change.  If
there is a rogue libinproctrace.so in /usr/lib on the target and we fail
to download ours, it might cover up a test failure.  But that situation
is probably still better than the original one, where it wasn't possible
to test remotely using the IPA at all.

[1] https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=6e774b13c3b81ac2599812adf058796948ce7e95

gdb/testsuite/ChangeLog:

	* gdb.arch/ftrace-insn-reloc.exp: Save gdb_load_shlib result,
	use it in info sharedlibrary test.
	* gdb.trace/ftrace-lock.exp: Likewise.
	* gdb.trace/ftrace.exp: Likewise.
	* gdb.trace/range-stepping.exp: Likewise.
	* gdb.trace/trace-break.exp: Likewise.
	* gdb.trace/trace-condition.exp: Likewise.
	* gdb.trace/trace-mt.exp: Likewise.